FIBK

fibk-20260128false000086041300008604132026-01-282026-01-28

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of report (date of earliest event reported): January 28, 2026

FIRST INTERSTATE BANCSYSTEM, INC.

(Exact name of registrant as specified in its charter)

Delaware001-34653 81-0331430 (State or other jurisdiction of incorporation or organization)(Commission File No.) (IRS Employer Identification No.)

401 North 31st Street

Billings, MT 59101 (Address of principal executive offices)(zip code)

(406)255-5311 (Registrant’s telephone number, including area code)

Not Applicable (Former name or former address, if changed since last report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2. below): ☐ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425) ☐ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a- 12) ☐ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b)) ☐ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

* * * * * Securities registered pursuant to Section 12(b) of the Act:

Title of each classTrading Symbol(s)Name of exchange on which registered Common stock, $0.00001 par valueFIBKNASDAQ

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter). Emerging growth company ☐ If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐ * * * * *

Item 2.02 Results of Operations and Financial Condition. On January 28, 2026, First Interstate BancSystem, Inc. (the “Company”) issued a press release regarding its financial results for the quarter ended December 31, 2025. A copy of the press release is furnished herewith as Exhibit 99.1 and is incorporated by reference herein. Neither the information included or incorporated by reference under this Item 2.02, nor the press release furnished herewith, shall be deemed to be “filed” for purposes of Section 18 of the Securities Exchange Act of 1934 (the “Exchange Act”) or incorporated by reference into any registration statement or other document filed pursuant to the Securities Act of 1933 (the “Securities Act”) or the Exchange Act, except as expressly set forth by specific reference in such filing.

Item 7.01 Regulation FD Disclosure. On January 28, 2026, the Company posted a new corporate presentation (the “Presentation”) on the Events & Presentations page of the Company’s website at https://www.fibk.com. The Presentation, which is furnished with this Current Report as Exhibit 99.2 and incorporated herein by reference, updates previously furnished presentations and provides an overview of the Company and its operations. Neither the information included or incorporated by reference under this Item 7.01, nor the Presentation furnished herewith, shall be deemed to be “filed” for purposes of Section 18 of the Exchange Act or incorporated by reference into any filing under the Securities Act or the Exchange Act, except as expressly set forth by specific reference in such a filing.

Item 8.01 Other Events. On January 28, 2026, the Company also announced that the Board of Directors of the Company declared, on January 27, 2026, a dividend of $0.47 per share, that is payable February 20, 2026 to shareholders of record of the Company as of February 10, 2026.

Item 9.01 Financial Statements and Exhibits.

(d)Exhibit NumberDescription

99.1 Press Release dated January 28, 2026.

99.2

Presentation

104Cover Page Interactive Data File (embedded within Inline XBRL document).

SIGNATURES

Pursuant to the requirements of the Securities and Exchange Act of 1934, the Registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized. Date: January 28, 2026

FIRST INTERSTATE BANCSYSTEM, INC.

By:/s/ JAMES A. REUTER James A. Reuter President and Chief Executive Officer

fibk-20251029false000086041300008604132025-10-292025-10-29

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of report (date of earliest event reported): October 29, 2025

FIRST INTERSTATE BANCSYSTEM, INC.

(Exact name of registrant as specified in its charter)

Delaware001-34653 81-0331430 (State or other jurisdiction of incorporation or organization)(Commission File No.) (IRS Employer Identification No.)

401 North 31st Street

Billings, MT 59101 (Address of principal executive offices)(zip code)

(406)255-5311 (Registrant’s telephone number, including area code)

Not Applicable (Former name or former address, if changed since last report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2. below): ☐ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425) ☐ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a- 12) ☐ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b)) ☐ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

* * * * * Securities registered pursuant to Section 12(b) of the Act:

Title of each classTrading Symbol(s)Name of exchange on which registered Common stock, $0.00001 par valueFIBKNASDAQ

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter). Emerging growth company ☐ If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐ * * * * *

Item 2.02 Results of Operations and Financial Condition. On October 29, 2025, First Interstate BancSystem, Inc. (the “Company”) issued a press release regarding its financial results for the quarter ended September 30, 2025. A copy of the press release is furnished herewith as Exhibit 99.1 and is incorporated by reference herein. Neither the information included or incorporated by reference under this Item 2.02, nor the press release furnished herewith, shall be deemed to be “filed” for purposes of Section 18 of the Securities Exchange Act of 1934 (the “Exchange Act”) or incorporated by reference into any registration statement or other document filed pursuant to the Securities Act of 1933 (the “Securities Act”) or the Exchange Act, except as expressly set forth by specific reference in such filing.

Item 7.01 Regulation FD Disclosure. On October 29, 2025, the Company posted a new corporate presentation (the “Presentation”) on the Events & Presentations page of the Company’s website at https://www.fibk.com. The Presentation, which is furnished with this Current Report as Exhibit 99.2 and incorporated herein by reference, updates previously furnished presentations and provides an overview of the Company and its operations. Neither the information included or incorporated by reference under this Item 7.01, nor the Presentation furnished herewith, shall be deemed to be “filed” for purposes of Section 18 of the Exchange Act or incorporated by reference into any filing under the Securities Act or the Exchange Act, except as expressly set forth by specific reference in such a filing.

Item 8.01 Other Events. On October 29, 2025, the Company also announced that the Board of Directors of the Company declared, on October 28, 2025, a dividend of $0.47 per share, that is payable November 20, 2025 to shareholders of record of the Company as of November 10, 2025.

Item 9.01 Financial Statements and Exhibits.

(d)Exhibit NumberDescription

99.1 Press Release dated October 29, 2025.

99.2

Presentation

104Cover Page Interactive Data File (embedded within Inline XBRL document).

SIGNATURES

Pursuant to the requirements of the Securities and Exchange Act of 1934, the Registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized. Date: October 29, 2025

FIRST INTERSTATE BANCSYSTEM, INC.

By:/s/ JAMES A. REUTER James A. Reuter President and Chief Executive Officer

fibk-20250729false000086041300008604132025-07-292025-07-29

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of report (date of earliest event reported): July 29, 2025

FIRST INTERSTATE BANCSYSTEM, INC.

(Exact name of registrant as specified in its charter)

Delaware001-34653 81-0331430 (State or other jurisdiction of incorporation or organization)(Commission File No.) (IRS Employer Identification No.)

401 North 31st Street

Billings, MT 59101 (Address of principal executive offices)(zip code)

(406)255-5311 (Registrant’s telephone number, including area code)

Not Applicable (Former name or former address, if changed since last report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2. below): ☐ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425) ☐ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a- 12) ☐ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b)) ☐ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

* * * * * Securities registered pursuant to Section 12(b) of the Act:

Title of each classTrading Symbol(s)Name of exchange on which registered Common stock, $0.00001 par valueFIBKNASDAQ

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter). Emerging growth company ☐ If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐ * * * * *

Item 2.02 Results of Operations and Financial Condition. On July 29, 2025, First Interstate BancSystem, Inc. (the “Company”) issued a press release regarding its financial results for the quarter ended June 30, 2025. A copy of the press release is furnished herewith as Exhibit 99.1 and is incorporated by reference herein. Neither the information included or incorporated by reference under this Item 2.02, nor the press release furnished herewith, shall be deemed to be “filed” for purposes of Section 18 of the Securities Exchange Act of 1934 (the “Exchange Act”) or incorporated by reference into any registration statement or other document filed pursuant to the Securities Act of 1933 (the “Securities Act”) or the Exchange Act, except as expressly set forth by specific reference in such filing.

Item 7.01 Regulation FD Disclosure. On July 29, 2025, the Company posted a new corporate presentation (the “Presentation”) on the Events & Presentations page of the Company’s website at https://www.fibk.com. The Presentation, which is furnished with this Current Report as Exhibit 99.2 and incorporated herein by reference, updates previously furnished presentations and provides an overview of the Company and its operations. Neither the information included or incorporated by reference under this Item 7.01, nor the Presentation furnished herewith, shall be deemed to be “filed” for purposes of Section 18 of the Exchange Act or incorporated by reference into any filing under the Securities Act or the Exchange Act, except as expressly set forth by specific reference in such a filing.

Item 8.01 Other Events. On July 29, 2025, the Company also announced that the Board of Directors of the Company declared, on July 28, 2025, a dividend of $0.47 per share, that is payable August 21, 2025 to shareholders of record of the Company as of August 11, 2025.

Item 9.01 Financial Statements and Exhibits.

(d)Exhibit NumberDescription

99.1 Press Release dated July 29, 2025.

99.2

Presentation

104Cover Page Interactive Data File (embedded within Inline XBRL document).

SIGNATURES

Pursuant to the requirements of the Securities and Exchange Act of 1934, the Registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized. Date: July 29, 2025

FIRST INTERSTATE BANCSYSTEM, INC.

By:/s/ JAMES A. REUTER James A. Reuter President and Chief Executive Officer

fibk-20250429false000086041300008604132025-04-292025-04-29

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of report (date of earliest event reported): April 29, 2025

FIRST INTERSTATE BANCSYSTEM, INC.

(Exact name of registrant as specified in its charter)

Delaware001-34653 81-0331430 (State or other jurisdiction of incorporation or organization)(Commission File No.) (IRS Employer Identification No.)

401 North 31st Street

Billings, MT 59101 (Address of principal executive offices)(zip code)

(406)255-5311 (Registrant’s telephone number, including area code)

Not Applicable (Former name or former address, if changed since last report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2. below): ☐ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425) ☐ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a- 12) ☐ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b)) ☐ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

* * * * * Securities registered pursuant to Section 12(b) of the Act:

Title of each classTrading Symbol(s)Name of exchange on which registered Common stock, $0.00001 par valueFIBKNASDAQ

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter). Emerging growth company ☐ If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐ * * * * *

Item 2.02 Results of Operations and Financial Condition. On April 29, 2025, First Interstate BancSystem, Inc. (the “Company”) issued a press release regarding its financial results for the quarter ended March 31, 2025. A copy of the press release is furnished herewith as Exhibit 99.1 and is incorporated by reference herein. Neither the information included or incorporated by reference under this Item 2.02, nor the press release furnished herewith, shall be deemed to be “filed” for purposes of Section 18 of the Securities Exchange Act of 1934 (the “Exchange Act”) or incorporated by reference into any registration statement or other document filed pursuant to the Securities Act of 1933 (the “Securities Act”) or the Exchange Act, except as expressly set forth by specific reference in such filing.

Item 7.01 Regulation FD Disclosure. On April 29, 2025, the Company posted a new corporate presentation (the “Presentation”) on the Events & Presentations page of the Company’s website at https://www.fibk.com. The Presentation, which is furnished with this Current Report as Exhibit 99.2 and incorporated herein by reference, updates previously furnished presentations and provides an overview of the Company and its operations. Neither the information included or incorporated by reference under this Item 7.01, nor the Presentation furnished herewith, shall be deemed to be “filed” for purposes of Section 18 of the Exchange Act or incorporated by reference into any filing under the Securities Act or the Exchange Act, except as expressly set forth by specific reference in such a filing.

Item 8.01 Other Events. On April 29, 2025, the Company also announced that the Board of Directors of the Company declared, on April 28, 2025, a dividend of $0.47 per share, that is payable May 22, 2025 to shareholders of record of the Company as of May 12, 2025.

Item 9.01 Financial Statements and Exhibits.

(d)Exhibit NumberDescription

99.1 Press Release dated April 29, 2025.

99.2

Presentation

104Cover Page Interactive Data File (embedded within Inline XBRL document).

SIGNATURES

Pursuant to the requirements of the Securities and Exchange Act of 1934, the Registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized. Date: April 29, 2025

FIRST INTERSTATE BANCSYSTEM, INC.

By:/s/ JAMES A. REUTER James A. Reuter President and Chief Executive Officer

fibk-20250129false000086041300008604132025-01-292025-01-29

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of report (date of earliest event reported): January 29, 2025

FIRST INTERSTATE BANCSYSTEM, INC.

(Exact name of registrant as specified in its charter)

Delaware001-34653 81-0331430 (State or other jurisdiction of incorporation or organization)(Commission File No.) (IRS Employer Identification No.)

401 North 31st Street

Billings, MT 59101 (Address of principal executive offices)(zip code)

(406)255-5311 (Registrant’s telephone number, including area code)

Not Applicable (Former name or former address, if changed since last report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2. below): ☐ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425) ☐ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a- 12) ☐ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b)) ☐ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

* * * * * Securities registered pursuant to Section 12(b) of the Act:

Title of each classTrading Symbol(s)Name of exchange on which registered Common stock, $0.00001 par valueFIBKNASDAQ

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter). Emerging growth company ☐ If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐ * * * * *

Item 2.02 Results of Operations and Financial Condition. On January 29, 2025, First Interstate BancSystem, Inc. (the “Company”) issued a press release regarding its financial results for the quarter ended December 31, 2024. A copy of the press release is furnished herewith as Exhibit 99.1 and is incorporated by reference herein. Neither the information included or incorporated by reference under this Item 2.02, nor the press release furnished herewith, shall be deemed to be “filed” for purposes of Section 18 of the Securities Exchange Act of 1934 (the “Exchange Act”) or incorporated by reference into any registration statement or other document filed pursuant to the Securities Act of 1933 (the “Securities Act”) or the Exchange Act, except as expressly set forth by specific reference in such filing.

Item 7.01 Regulation FD Disclosure. On January 29, 2025, the Company posted a new corporate presentation (the “Presentation”) on the Events & Presentations page of the Company’s website at https://www.fibk.com. The Presentation, which is furnished with this Current Report as Exhibit 99.2 and incorporated herein by reference, updates previously furnished presentations and provides an overview of the Company and its operations. Neither the information included or incorporated by reference under this Item 7.01, nor the Presentation furnished herewith, shall be deemed to be “filed” for purposes of Section 18 of the Exchange Act or incorporated by reference into any filing under the Securities Act or the Exchange Act, except as expressly set forth by specific reference in such a filing.

Item 8.01 Other Events. On January 29, 2025, the Company also announced that the Board of Directors of the Company declared, on January 28, 2025, a dividend of $0.47 per share, that is payable February 20, 2025 to shareholders of record of the Company as of February 10, 2025.

Item 9.01 Financial Statements and Exhibits.

(d)Exhibit NumberDescription

99.1 Press Release dated January 29, 2025.

99.2

Presentation

104Cover Page Interactive Data File (embedded within Inline XBRL document).

SIGNATURES

Pursuant to the requirements of the Securities and Exchange Act of 1934, the Registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized. Date: January 29, 2025

FIRST INTERSTATE BANCSYSTEM, INC.

By:/s/ JAMES A. REUTER James A. Reuter President and Chief Executive Officer

fibk-20250103false000086041300008604132025-01-032025-01-03

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of report (date of earliest event reported): January 3, 2025

FIRST INTERSTATE BANCSYSTEM, INC.

(Exact name of registrant as specified in its charter)

Delaware001-34653 81-0331430 (State or other jurisdiction of incorporation or organization)(Commission File No.) (IRS Employer Identification No.)

401 North 31st Street

Billings, MT 59101 (Address of principal executive offices)(zip code)

(406)255-5311 (Registrant’s telephone number, including area code)

Not Applicable (Former name or former address, if changed since last report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2. below): ☐ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425) ☐ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a- 12) ☐ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b)) ☐ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

* * * * * Securities registered pursuant to Section 12(b) of the Act:

Title of each classTrading Symbol(s)Name of exchange on which registered Common stock, $0.00001 par valueFIBKNASDAQ

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter). Emerging growth company ☐ If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐ * * * * *

Item 2.02 Results of Operations and Financial Condition. The information in Item 2.06 of this Current Report on Form 8-K (the “Report”) is incorporated herein by reference. Item 2.06 Material Impairments. On January 3, 2025, management of First Interstate BancSystem, Inc. (the “Company”) and its wholly owned subsidiary First Interstate Bank (the “Bank”) determined that the Company expects to recognize a material, partial charge-off of approximately $49.3 million for the quarter ended December 31, 2024 related to a single commercial and industrial loan relationship (the “C&I Loan”), for which a $26.5 million specific reserve was held as of September 30, 2024. As of December 31, 2024, the outstanding aggregate balance of the C&I Loan was approximately $62.8 million. As previously disclosed with respect to the C&I Loan, the Bank placed the loan relationship on non-accrual status in the first quarter of 2024. As a result of adverse developments impacting the borrower’s business, including the continued deterioration of the borrower’s financial performance in the fourth quarter of 2024, a careful review of the available collateral and other developments, and the borrower’s failure to perform under a forbearance agreement, including its failure to consummate a proposed sale of its assets prior to December 31, 2024 in accordance with a mutually agreed upon market and sale process, the Company initiated proceedings against the borrower and certain of its affiliates on January 3, 2025 seeking, among other things, the appointment of a receiver over the borrower and its assets on an emergency basis and to enforce its rights under the applicable loan documents. On January 6, 2025, a receiver was appointed by a court on an emergency basis. On January 8, 2025, the borrower, under the control of the receiver, entered into an asset purchase agreement with a third-party buyer pursuant to which the borrower has agreed to sell substantially all of its assets to the buyer. Closing of this transaction is expected to occur in January 2025, subject to various closing conditions, including court approval of the Purchase Agreement. If consummated, proceeds received by the borrower pursuant to the Purchase Agreement are expected to be applied to resolve the C&I Loan, as further described below. The C&I Loan is secured by all of the borrower’s assets. As of the date of this Report, based on the estimated realizable value to the Company pursuant to the terms of the Purchase Agreement, the Company’s remaining exposure of $13.5 million is the Company’s best estimate of proceeds expected to be received by the Company at this time. The Company is currently unable to quantify the amount of potential recoveries in excess of what is reflected in the current charge-off esti

fibk-20241024false000086041300008604132024-10-242024-10-24

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of report (date of earliest event reported): October 24, 2024

FIRST INTERSTATE BANCSYSTEM, INC.

(Exact name of registrant as specified in its charter)

Delaware001-34653 81-0331430 (State or other jurisdiction of incorporation or organization)(Commission File No.) (IRS Employer Identification No.)

401 North 31st Street

Billings, MT 59101 (Address of principal executive offices)(zip code)

(406)255-5311 (Registrant’s telephone number, including area code)

Not Applicable (Former name or former address, if changed since last report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2. below): ☐ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425) ☐ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a- 12) ☐ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b)) ☐ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

* * * * * Securities registered pursuant to Section 12(b) of the Act:

Title of each classTrading Symbol(s)Name of exchange on which registered Common stock, $0.00001 par valueFIBKNASDAQ

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter). Emerging growth company ☐ If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐ * * * * *

Item 2.02 Results of Operations and Financial Condition. On October 24, 2024, First Interstate BancSystem, Inc. (the “Company”) issued a press release regarding its financial results for the quarter ended September 30, 2024. A copy of the press release is furnished herewith as Exhibit 99.1 and is incorporated by reference herein. Neither the information included or incorporated by reference under this Item 2.02, nor the press release furnished herewith, shall be deemed to be “filed” for purposes of Section 18 of the Securities Exchange Act of 1934 (the “Exchange Act”) or incorporated by reference into any registration statement or other document filed pursuant to the Securities Act of 1933 (the “Securities Act”) or the Exchange Act, except as expressly set forth by specific reference in such filing.

Item 7.01 Regulation FD Disclosure. On October 24, 2024, the Company posted a new corporate presentation (the “Presentation”) on the Events & Presentations page of the Company’s website at https://www.fibk.com. The Presentation, which is furnished with this Current Report as Exhibit 99.2 and incorporated herein by reference, updates previously furnished presentations and provides an overview of the Company and its operations. Neither the information included or incorporated by reference under this Item 7.01, nor the Presentation furnished herewith, shall be deemed to be “filed” for purposes of Section 18 of the Exchange Act or incorporated by reference into any filing under the Securities Act or the Exchange Act, except as expressly set forth by specific reference in such a filing.

Item 8.01 Other Events. On October 24, 2024, the Company also announced that the Board of Directors of the Company declared, on October 23, 2024, a dividend of $0.47 per share, that is payable November 14, 2024 to shareholders of record of the Company as of November 4, 2024.

Item 9.01 Financial Statements and Exhibits.

(d)Exhibit NumberDescription

99.1 Press Release dated October 24, 2024.

99.2

Presentation

104Cover Page Interactive Data File (embedded within Inline XBRL document).

SIGNATURES

Pursuant to the requirements of the Securities and Exchange Act of 1934, the Registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized. Date: October 24, 2024

FIRST INTERSTATE BANCSYSTEM, INC.

By:/s/ KEVIN P. RILEY Kevin P. Riley President and Chief Executive Officer

fibk-20240725false000086041300008604132024-07-252024-07-25

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of report (date of earliest event reported): July 25, 2024

FIRST INTERSTATE BANCSYSTEM, INC.

(Exact name of registrant as specified in its charter)

Delaware001-34653 81-0331430 (State or other jurisdiction of incorporation or organization)(Commission File No.) (IRS Employer Identification No.)

401 North 31st Street

Billings, MT 59101 (Address of principal executive offices)(zip code)

(406)255-5311 (Registrant’s telephone number, including area code)

Not Applicable (Former name or former address, if changed since last report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2. below): ☐ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425) ☐ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a- 12) ☐ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b)) ☐ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

* * * * * Securities registered pursuant to Section 12(b) of the Act:

Title of each classTrading Symbol(s)Name of exchange on which registered Common stock, $0.00001 par valueFIBKNASDAQ

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter). Emerging growth company ☐ If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐ * * * * *

Item 2.02 Results of Operations and Financial Condition. On July 25, 2024, First Interstate BancSystem, Inc. (the “Company”) issued a press release regarding its financial results for the quarter ended June 30, 2024. A copy of the press release is furnished herewith as Exhibit 99.1 and is incorporated by reference herein. Neither the information included or incorporated by reference under this Item 2.02, nor the press release furnished herewith, shall be deemed to be “filed” for purposes of Section 18 of the Securities Exchange Act of 1934 (the “Exchange Act”) or incorporated by reference into any registration statement or other document filed pursuant to the Securities Act of 1933 (the “Securities Act”) or the Exchange Act, except as expressly set forth by specific reference in such filing.

Item 7.01 Regulation FD Disclosure. On July 25, 2024, the Company posted a new corporate presentation (the “Presentation”) on the Events & Presentations page of the Company’s website at https://www.fibk.com. The Presentation, which is furnished with this Current Report as Exhibit 99.2 and incorporated herein by reference, updates previously furnished presentations and provides an overview of the Company and its operations. Neither the information included or incorporated by reference under this Item 7.01, nor the Presentation furnished herewith, shall be deemed to be “filed” for purposes of Section 18 of the Exchange Act or incorporated by reference into any filing under the Securities Act or the Exchange Act, except as expressly set forth by specific reference in such a filing.

Item 8.01 Other Events. On July 25, 2024, the Company also announced that the Board of Directors of the Company declared, on July 24, 2024, a dividend of $0.47 per share, that is payable August 15, 2024 to shareholders of record of the Company as of August 5, 2024.

Item 9.01 Financial Statements and Exhibits.

(d)Exhibit NumberDescription

99.1 Press Release dated July 25, 2024.

99.2

Presentation

104Cover Page Interactive Data File (embedded within Inline XBRL document).

SIGNATURES

Pursuant to the requirements of the Securities and Exchange Act of 1934, the Registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized. Date: July 25, 2024

FIRST INTERSTATE BANCSYSTEM, INC.

By:/s/ KEVIN P. RILEY Kevin P. Riley President and Chief Executive Officer

fibk-20240424false000086041300008604132024-04-242024-04-24

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of report (date of earliest event reported): April 24, 2024

FIRST INTERSTATE BANCSYSTEM, INC.

(Exact name of registrant as specified in its charter)

Delaware001-34653 81-0331430 (State or other jurisdiction of incorporation or organization)(Commission File No.) (IRS Employer Identification No.)

401 North 31st Street

Billings, MT 59101 (Address of principal executive offices)(zip code)

(406)255-5311 (Registrant’s telephone number, including area code)

Not Applicable (Former name or former address, if changed since last report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2. below): ☐ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425) ☐ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a- 12) ☐ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b)) ☐ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

* * * * * Securities registered pursuant to Section 12(b) of the Act:

Title of each classTrading Symbol(s)Name of exchange on which registered Common stock, $0.00001 par valueFIBKNASDAQ

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter). Emerging growth company ☐ If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐ * * * * *

Item 2.02 Results of Operations and Financial Condition. On April 24, 2024, First Interstate BancSystem, Inc. (the “Company”) issued a press release regarding its financial results for the quarter ended March 31, 2024. A copy of the press release is furnished herewith as Exhibit 99.1 and is incorporated by reference herein. Neither the information included or incorporated by reference under this Item 2.02, nor the press release furnished herewith, shall be deemed to be “filed” for purposes of Section 18 of the Securities Exchange Act of 1934 (the “Exchange Act”) or incorporated by reference into any registration statement or other document filed pursuant to the Securities Act of 1933 (the “Securities Act”) or the Exchange Act, except as expressly set forth by specific reference in such filing.

Item 7.01 Regulation FD Disclosure. On April 24, 2024, the Company posted a new corporate presentation (the “Presentation”) on the Events & Presentations page of the Company’s website at https://www.fibk.com. The Presentation, which is furnished with this Current Report as Exhibit 99.2 and incorporated herein by reference, updates previously furnished presentations and provides an overview of the Company and its operations. Neither the information included or incorporated by reference under this Item 7.01, nor the Presentation furnished herewith, shall be deemed to be “filed” for purposes of Section 18 of the Exchange Act or incorporated by reference into any filing under the Securities Act or the Exchange Act, except as expressly set forth by specific reference in such a filing.

Item 8.01 Other Events. On April 24, 2024, the Company also announced that the Board of Directors of the Company declared, on April 23, 2024, a dividend of $0.47 per share, that is payable May 16, 2024 to shareholders of record of the Company as of May 6, 2024.

Item 9.01 Financial Statements and Exhibits.

(d)Exhibit NumberDescription

99.1 Press Release dated April 24, 2024.

99.2

Presentation

104Cover Page Interactive Data File (embedded within Inline XBRL document).

SIGNATURES

Pursuant to the requirements of the Securities and Exchange Act of 1934, the Registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized. Date: April 24, 2024

FIRST INTERSTATE BANCSYSTEM, INC.

By:/s/ KEVIN P. RILEY Kevin P. Riley President and Chief Executive Officer

fibk-20240130false000086041300008604132024-01-302024-01-30

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of report (date of earliest event reported): January 30, 2024

FIRST INTERSTATE BANCSYSTEM, INC.

(Exact name of registrant as specified in its charter)

Delaware001-34653 81-0331430 (State or other jurisdiction of incorporation or organization)(Commission File No.) (IRS Employer Identification No.)

401 North 31st Street

Billings, MT 59101 (Address of principal executive offices)(zip code)

(406)255-5311 (Registrant’s telephone number, including area code)

Not Applicable (Former name or former address, if changed since last report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2. below): ☐ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425) ☐ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a- 12) ☐ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b)) ☐ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

* * * * * Securities registered pursuant to Section 12(b) of the Act:

Title of each classTrading Symbol(s)Name of exchange on which registered Common stock, $0.00001 par valueFIBKNASDAQ

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter). Emerging growth company ☐ If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐ * * * * *

Item 2.02 Results of Operations and Financial Condition. On January 30, 2024, First Interstate BancSystem, Inc. (the “Company”) issued a press release regarding its financial results for the quarter ended December 31, 2023. A copy of the press release is furnished herewith as Exhibit 99.1 and is incorporated by reference herein. Neither the information included or incorporated by reference under this Item 2.02, nor the press release furnished herewith, shall be deemed to be “filed” for purposes of Section 18 of the Securities Exchange Act of 1934 (the “Exchange Act”) or incorporated by reference into any registration statement or other document filed pursuant to the Securities Act of 1933 (the “Securities Act”) or the Exchange Act, except as expressly set forth by specific reference in such filing.

Item 7.01 Regulation FD Disclosure. On January 30, 2024, the Company posted a new corporate presentation (the “Presentation”) on the News and Events page of the Company’s website at https://www.fibk.com. The Presentation, which is furnished with this Current Report as Exhibit 99.2 and incorporated herein by reference, updates previously furnished presentations and provides an overview of the Company and its operations. Neither the information included or incorporated by reference under this Item 7.01, nor the Presentation furnished herewith, shall be deemed to be “filed” for purposes of Section 18 of the Securities Exchange Act or incorporated by reference into any filing under the Securities Act or the Exchange Act, except as expressly set forth by specific reference in such a filing.

Item 8.01 Other Events. On January 30, 2024, the Company also announced that the Board of Directors of the Company declared, on January 26, 2024, a dividend of $0.47 per share, that is payable February 19, 2024 to shareholders of record of the Company as of February 9, 2024.

Item 9.01 Financial Statements and Exhibits.

(d)Exhibit NumberDescription

99.1 Press Release dated January 30, 2024.

99.2

Presentation

104Cover Page Interactive Data File (embedded within Inline XBRL document).

SIGNATURES

Pursuant to the requirements of the Securities and Exchange Act of 1934, the Registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized. Date: January 30, 2024

FIRST INTERSTATE BANCSYSTEM, INC.

By:/s/ KEVIN P. RILEY Kevin P. Riley President and Chief Executive Officer

fibk-20231025false000086041300008604132023-10-252023-10-25

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of report (date of earliest event reported): October 25, 2023

FIRST INTERSTATE BANCSYSTEM, INC.

(Exact name of registrant as specified in its charter)

Delaware001-34653 81-0331430 (State or other jurisdiction of incorporation or organization)(Commission File No.) (IRS Employer Identification No.)

401 North 31st Street

Billings, MT 59101 (Address of principal executive offices)(zip code)

(406)255-5311 (Registrant’s telephone number, including area code)

Not Applicable (Former name or former address, if changed since last report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2. below): ☐ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425) ☐ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a- 12) ☐ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b)) ☐ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

* * * * * Securities registered pursuant to Section 12(b) of the Act:

Title of each classTrading Symbol(s)Name of exchange on which registered Common stock, $0.00001 par valueFIBKNASDAQ

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter). Emerging growth company ☐ If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐ * * * * *

Item 2.02 Results of Operations and Financial Condition. On October 25, 2023, First Interstate BancSystem, Inc. (the “Company”) issued a press release regarding its financial results for the quarter ended September 30, 2023. A copy of the press release is furnished herewith as Exhibit 99.1 and is incorporated by reference herein. Neither the information included or incorporated by reference under this Item 2.02, nor the press release furnished herewith, shall be deemed to be “filed” for purposes of Section 18 of the Securities Exchange Act of 1934 (the “Exchange Act”) or incorporated by reference into any registration statement or other document filed pursuant to the Securities Act of 1933 (the “Securities Act”) or the Exchange Act, except as expressly set forth by specific reference in such filing.

Item 7.01 Regulation FD Disclosure. On October 25, 2023, the Company posted a new corporate presentation (the “Presentation”) on the News and Events page of the Company’s website at https://www.fibk.com. The Presentation, which is furnished with this Current Report as Exhibit 99.2 and incorporated herein by reference, updates previously furnished presentations and provides an overview of the Company and its operations. Neither the information included or incorporated by reference under this Item 7.01, nor the Presentation furnished herewith, shall be deemed to be “filed” for purposes of Section 18 of the Securities Exchange Act or incorporated by reference into any filing under the Securities Act or the Exchange Act, except as expressly set forth by specific reference in such a filing.

Item 8.01 Other Events. On October 25, 2023, the Company also announced that the Board of Directors of the Company declared, on October 24, 2023, a dividend of $0.47 per share, that is payable November 16, 2023 to shareholders of record of the Company as of November 6, 2023.

Item 9.01 Financial Statements and Exhibits.

(d)Exhibit NumberDescription

99.1 Press Release dated October 25, 2023.

99.2

Presentation

104Cover Page Interactive Data File (embedded within Inline XBRL document).

SIGNATURES

Pursuant to the requirements of the Securities and Exchange Act of 1934, the Registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized. Date: October 25, 2023

FIRST INTERSTATE BANCSYSTEM, INC.

By:/s/ KEVIN P. RILEY Kevin P. Riley President and Chief Executive Officer

fibk-20230726false000086041300008604132023-07-262023-07-26

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of report (date of earliest event reported): July 26, 2023

FIRST INTERSTATE BANCSYSTEM, INC.

(Exact name of registrant as specified in its charter)

Delaware001-34653 81-0331430 (State or other jurisdiction of incorporation or organization)(Commission File No.) (IRS Employer Identification No.)

401 North 31st Street

Billings, MT 59101 (Address of principal executive offices)(zip code)

(406)255-5311 (Registrant’s telephone number, including area code)

Not Applicable (Former name or former address, if changed since last report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2. below): ☐ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425) ☐ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a- 12) ☐ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b)) ☐ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

* * * * * Securities registered pursuant to Section 12(b) of the Act:

Title of each classTrading Symbol(s)Name of exchange on which registered Class A common stock, $0.00001 par valueFIBKNASDAQ

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter). Emerging growth company ☐ If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐ * * * * *

Item 2.02 Results of Operations and Financial Condition. On July 26, 2023, First Interstate BancSystem, Inc. (the “Company”) issued a press release regarding its financial results for the quarter ended June 30, 2023. A copy of the press release is furnished herewith as Exhibit 99.1 and is incorporated by reference herein. Neither the information included or incorporated by reference under this Item 2.02, nor the press release furnished herewith, shall be deemed to be “filed” for purposes of Section 18 of the Securities Exchange Act of 1934 (the “Exchange Act”) or incorporated by reference into any registration statement or other document filed pursuant to the Securities Act of 1933 (the “Securities Act”) or the Exchange Act, except as expressly set forth by specific reference in such filing.

Item 7.01 Regulation FD Disclosure. On July 26, 2023, the Company posted a new corporate presentation (the “Presentation”) on the News and Events page of the Company’s website at https://www.fibk.com. The Presentation, which is furnished with this Current Report as Exhibit 99.2 and incorporated herein by reference, updates previously furnished presentations and provides an overview of the Company and its operations. Neither the information included or incorporated by reference under this Item 7.01, nor the Presentation furnished herewith, shall be deemed to be “filed” for purposes of Section 18 of the Securities Exchange Act or incorporated by reference into any filing under the Securities Act or the Exchange Act, except as expressly set forth by specific reference in such a filing.

Item 8.01 Other Events. On July 26, 2023, the Company also announced that the Board of Directors of the Company declared, on July 25, 2023, a dividend of $0.47 per share, that is payable August 17, 2023 to shareholders of record of the Company as of August 7, 2023.

Item 9.01 Financial Statements and Exhibits.

(d)Exhibit NumberDescription

99.1 Press Release dated July 26, 2023.

99.2

Presentation

104Cover Page Interactive Data File (embedded within Inline XBRL document).

SIGNATURES

Pursuant to the requirements of the Securities and Exchange Act of 1934, the Registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized. Date: July 26, 2023

FIRST INTERSTATE BANCSYSTEM, INC.

By:/s/ KEVIN P. RILEY Kevin P. Riley President and Chief Executive Officer

fibk-20230524false000086041300008604132023-05-242023-05-24

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of report (date of earliest event reported): May 24, 2023

FIRST INTERSTATE BANCSYSTEM, INC.

(Exact name of registrant as specified in its charter)

Delaware001-34653 81-0331430 (State or other jurisdiction of incorporation or organization)(Commission File No.) (IRS Employer Identification No.)

401 North 31st Street

Billings, MT 59101 (Address of principal executive offices)(zip code)

(406)255-5311 (Registrant’s telephone number, including area code)

Not Applicable (Former name or former address, if changed since last report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2. below): ☐ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425) ☐ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a- 12) ☐ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b)) ☐ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

* * * * * Securities registered pursuant to Section 12(b) of the Act:

Title of each classTrading Symbol(s)Name of exchange on which registered Common stock, $0.00001 par valueFIBKNASDAQ

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter). Emerging growth company ☐ If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐ * * * * *

Item 2.02 Results of Operations and Financial Condition On May 24, 2023, the Registrant released its shareholder presentation associated with its annual meeting of shareholders (the “Presentation”) on the News and Events page on the Registrant’s Investor Relations website at https://www.fibk.com. The Presentation is being furnished under this Item 2.02 solely because it includes an additional presentation not previously provided by the Registrant of adjusted return on average assets for each of the completed fiscal years in the five years ended December 31, 2022. These financial measures are being furnished as additional information only and do not modify or change in any respect the previously reported financial results of the Registrant. The Presentation is furnished with this Current Report as Exhibit 99.1. Neither the information included or incorporated by reference under this Item 2.02, nor the Presentation furnished herewith, shall be deemed to be “filed” for purposes of Section 18 of the Securities Exchange Act of 1934 (the “Exchange Act”) or incorporated by reference into any registration statement or other document filed pursuant to the Securities Act of 1933 or the Exchange Act, except as expressly set forth by specific reference in such filing. Item 9.01 Financial Statements and Exhibits. (d) Exhibits.

(d)Exhibit No.Exhibit Description

99.1**

Presentation

104Cover Page Interactive Data File (formatted as inline XBRL document)

**Furnished herewith

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the Registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized. Date: May 25, 2023

FIRST INTERSTATE BANCSYSTEM, INC.

By:/s/ KEVIN P. RILEY Kevin P. Riley President and Chief Executive Officer

fibk-20230426false000086041300008604132023-04-262023-04-26

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of report (date of earliest event reported): April 26, 2023

FIRST INTERSTATE BANCSYSTEM, INC.

(Exact name of registrant as specified in its charter)

Montana001-34653 81-0331430 (State or other jurisdiction of incorporation or organization)(Commission File No.) (IRS Employer Identification No.)

401 North 31st Street

Billings, MT 59116-0918 (Address of principal executive offices)(zip code)

(406)255-5311 (Registrant’s telephone number, including area code)

Not Applicable (Former name or former address, if changed since last report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2. below): ☐ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425) ☐ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a- 12) ☐ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b)) ☐ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

* * * * * Securities registered pursuant to Section 12(b) of the Act:

Title of each classTrading Symbol(s)Name of exchange on which registered Class A common stock, no par valueFIBKNASDAQ

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter). Emerging growth company ☐ If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐ * * * * *

Item 2.02 Results of Operations and Financial Condition. On April 26, 2023, First Interstate BancSystem, Inc. (the “Company”) issued a press release regarding its financial results for the quarter ended March 31, 2023. A copy of the press release is furnished herewith as Exhibit 99.1 and is incorporated by reference herein. Neither the information included or incorporated by reference under this Item 2.02, nor the press release furnished herewith, shall be deemed to be “filed” for purposes of Section 18 of the Securities Exchange Act of 1934 (the “Exchange Act”) or incorporated by reference into any registration statement or other document filed pursuant to the Securities Act of 1933 (the “Securities Act”) or the Exchange Act, except as expressly set forth by specific reference in such filing.

Item 7.01 Regulation FD Disclosure. On April 26, 2023, the Company posted a new corporate presentation (the “Presentation”) on the News and Events page of the Company’s website at https://www.fibk.com. The Presentation, which is furnished with this Current Report as Exhibit 99.2 and incorporated herein by reference, updates previously furnished presentations and provides an overview of the Company and its operations. Neither the information included or incorporated by reference under this Item 7.01, nor the Presentation furnished herewith, shall be deemed to be “filed” for purposes of Section 18 of the Securities Exchange Act or incorporated by reference into any filing under the Securities Act or the Exchange Act, except as expressly set forth by specific reference in such a filing.

Item 8.01 Other Events. On April 26, 2023, the Company also announced that the Board of Directors of the Company declared, on April 25, 2023, a dividend of $0.47 per share, that is payable May 18, 2023 to shareholders of record of the Company as of May 8, 2023.

Item 9.01 Financial Statements and Exhibits.

(d)Exhibit NumberDescription

99.1 Press Release dated April 26, 2023.

99.2

Presentation

104Cover Page Interactive Data File (embedded within Inline XBRL document).

SIGNATURES

Pursuant to the requirements of the Securities and Exchange Act of 1934, the Registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized. Date: April 26, 2023

FIRST INTERSTATE BANCSYSTEM, INC.

By:/s/ KEVIN P. RILEY Kevin P. Riley President and Chief Executive Officer

fibk-20230126false000086041300008604132023-01-262023-01-26

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of report (date of earliest event reported): January 26, 2023

FIRST INTERSTATE BANCSYSTEM, INC.

(Exact name of registrant as specified in its charter)

Montana001-34653 81-0331430 (State or other jurisdiction of incorporation or organization)(Commission File No.) (IRS Employer Identification No.)

401 North 31st Street

Billings, MT 59116-0918 (Address of principal executive offices)(zip code)

(406)255-5311 (Registrant’s telephone number, including area code)

Not Applicable (Former name or former address, if changed since last report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2. below): ☐ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425) ☐ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a- 12) ☐ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b)) ☐ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

* * * * * Securities registered pursuant to Section 12(b) of the Act:

Title of each classTrading Symbol(s)Name of exchange on which registered Class A common stock, no par valueFIBKNASDAQ

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter). Emerging growth company ☐ If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐ * * * * *

Item 2.02 Results of Operations and Financial Condition. On January 26, 2023, First Interstate BancSystem, Inc. (the “Company”) issued a press release regarding its financial results for the quarter ended December 31, 2022. A copy of the press release is furnished herewith as Exhibit 99.1 and is incorporated by reference herein. Neither the information included or incorporated by reference under this Item 2.02, nor the press release furnished herewith, shall be deemed to be “filed” for purposes of Section 18 of the Securities Exchange Act of 1934 (the “Exchange Act”) or incorporated by reference into any registration statement or other document filed pursuant to the Securities Act of 1933 (the “Securities Act”) or the Exchange Act, except as expressly set forth by specific reference in such filing.

Item 7.01 Regulation FD Disclosure. On January 26, 2023, the Company posted a new corporate presentation (the “Presentation”) on the News and Events page of the Company’s website at https://www.fibk.com. The Presentation, which is furnished with this Current Report as Exhibit 99.2 and incorporated herein by reference, updates previously furnished presentations and provides an overview of the Company and its operations. Neither the information included or incorporated by reference under this Item 7.01, nor the Presentation furnished herewith, shall be deemed to be “filed” for purposes of Section 18 of the Securities Exchange Act or incorporated by reference into any filing under the Securities Act or the Exchange Act, except as expressly set forth by specific reference in such a filing.

Item 8.01 Other Events. On January 26, 2023, the Company also announced that the Board of Directors of the Company declared, on January 25, 2023, a dividend of $0.47 per share, that is payable February 17, 2023 to shareholders of record of the Company as of February 7, 2023.

Item 9.01 Financial Statements and Exhibits.

(d)Exhibit NumberDescription

99.1 Press Release dated January 26, 2023.

99.2

Presentation

104Cover Page Interactive Data File (embedded within Inline XBRL document).

SIGNATURES

Pursuant to the requirements of the Securities and Exchange Act of 1934, the Registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized. Date: January 26, 2023

FIRST INTERSTATE BANCSYSTEM, INC.

By:/s/ KEVIN P. RILEY Kevin P. Riley President and Chief Executive Officer

fibk-20221024false000086041300008604132022-10-242022-10-24

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of report (date of earliest event reported): October 24, 2022

FIRST INTERSTATE BANCSYSTEM, INC.

(Exact name of registrant as specified in its charter)

Montana001-34653 81-0331430 (State or other jurisdiction of incorporation or organization)(Commission File No.) (IRS Employer Identification No.)

401 North 31st Street

Billings, MT 59116-0918 (Address of principal executive offices)(zip code)

(406)255-5311 (Registrant’s telephone number, including area code)

Not Applicable (Former name or former address, if changed since last report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2. below): ☐ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425) ☐ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a- 12) ☐ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b)) ☐ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

* * * * * Securities registered pursuant to Section 12(b) of the Act:

Title of each classTrading Symbol(s)Name of exchange on which registered Class A common stock, no par valueFIBKNASDAQ

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter). Emerging growth company ☐ If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐ * * * * *

Item 2.02 Results of Operations and Financial Condition. On October 25, 2022, First Interstate BancSystem, Inc. (the “Company”) issued a press release regarding its financial results for the quarter ended September 30, 2022. A copy of the press release is furnished herewith as Exhibit 99.1 and is incorporated by reference herein. Neither the information included or incorporated by reference under this Item 2.02, nor the press release furnished herewith, shall be deemed to be “filed” for purposes of Section 18 of the Securities Exchange Act of 1934 (the “Exchange Act”) or incorporated by reference into any registration statement or other document filed pursuant to the Securities Act of 1933 (the “Securities Act”) or the Exchange Act, except as expressly set forth by specific reference in such filing.

Item 7.01 Regulation FD Disclosure. On October 25, 2022, the Company posted a new corporate presentation (the “Presentation”) on the News and Events page of the Company’s website at https://www.fibk.com. The Presentation, which is furnished with this Current Report as Exhibit 99.2 and incorporated herein by reference, updates previously furnished presentations and provides an overview of the Company and its operations. Neither the information included or incorporated by reference under this Item 7.01, nor the Presentation furnished herewith, shall be deemed to be “filed” for purposes of Section 18 of the Securities Exchange Act or incorporated by reference into any filing under the Securities Act or the Exchange Act, except as expressly set forth by specific reference in such a filing.

Item 8.01 Other Events. On October 25, 2022, the Company also announced that the Board of Directors of the Company declared, on October 24, 2022, a dividend of $0.47 per share, that is payable November 18, 2022 to shareholders of record of the Company as of November 8, 2022.

Item 9.01 Financial Statements and Exhibits.

(d)Exhibit NumberDescription

99.1 Press Release dated October 25, 2022.

99.2

Presentation

104Cover Page Interactive Data File (embedded within Inline XBRL document).

SIGNATURES

Pursuant to the requirements of the Securities and Exchange Act of 1934, the Registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized. Date: October 25, 2022

FIRST INTERSTATE BANCSYSTEM, INC.

By:/s/ KEVIN P. RILEY Kevin P. Riley President and Chief Executive Officer

fibk-20220726false000086041300008604132022-07-262022-07-26

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of report (date of earliest event reported): July 26, 2022

FIRST INTERSTATE BANCSYSTEM, INC.

(Exact name of registrant as specified in its charter)

Montana001-34653 81-0331430 (State or other jurisdiction of incorporation or organization)(Commission File No.) (IRS Employer Identification No.)

401 North 31st Street

Billings, MT 59116-0918 (Address of principal executive offices)(zip code)

(406)255-5311 (Registrant’s telephone number, including area code)

Not Applicable (Former name or former address, if changed since last report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2. below): ☐ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425) ☐ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a- 12) ☐ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b)) ☐ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

* * * * * Securities registered pursuant to Section 12(b) of the Act:

Title of each classTrading Symbol(s)Name of exchange on which registered Class A common stock, no par valueFIBKNASDAQ

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter). Emerging growth company ☐ If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐ * * * * *

Item 2.02 Results of Operations and Financial Condition. On July 26, 2022, First Interstate BancSystem, Inc. (the “Company”) issued a press release regarding its financial results for the quarter ended June 30, 2022. A copy of the press release is furnished herewith as Exhibit 99.1 and is incorporated by reference herein. Neither the information included or incorporated by reference under this Item 2.02, nor the press release furnished herewith, shall be deemed to be “filed” for purposes of Section 18 of the Securities Exchange Act of 1934 (the “Exchange Act”) or incorporated by reference into any registration statement or other document filed pursuant to the Securities Act of 1933 (the “Securities Act”) or the Exchange Act, except as expressly set forth by specific reference in such filing.

Item 7.01 Regulation FD Disclosure. On July 26, 2022, the Company posted a new corporate presentation (the “Presentation”) on the News and Events page of the Company’s website at https://www.fibk.com. The Presentation, which is furnished with this Current Report as Exhibit 99.2 and incorporated herein by reference, updates previously furnished presentations and provides an overview of the Company and its operations. Neither the information included or incorporated by reference under this Item 7.01, nor the Presentation furnished herewith, shall be deemed to be “filed” for purposes of Section 18 of the Securities Exchange Act or incorporated by reference into any filing under the Securities Act or the Exchange Act, except as expressly set forth by specific reference in such a filing.

Item 8.01 Other Events. On July 26, 2022, the Company also announced that the Board of Directors of the Company declared, on July 25, 2022, a dividend of $0.41 per share, that is payable August 19, 2022 to shareholders of record of the Company as of August 9, 2022.

Item 9.01 Financial Statements and Exhibits.

(d)Exhibit NumberDescription

99.1 Press Release dated July 26, 2022.

99.2

Presentation

104Cover Page Interactive Data File (embedded within Inline XBRL document).

SIGNATURES

Pursuant to the requirements of the Securities and Exchange Act of 1934, the Registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized. Date: July 26, 2022

FIRST INTERSTATE BANCSYSTEM, INC.

By:/s/ KEVIN P. RILEY Kevin P. Riley President and Chief Executive Officer

fibk-20220428false000086041300008604132022-04-282022-04-28

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of report (date of earliest event reported): April 28, 2022

FIRST INTERSTATE BANCSYSTEM, INC.

(Exact name of registrant as specified in its charter)

Montana001-34653 81-0331430 (State or other jurisdiction of incorporation or organization)(Commission File No.) (IRS Employer Identification No.)

401 North 31st Street

Billings, MT 59116-0918 (Address of principal executive offices)(zip code)

(406)255-5311 (Registrant’s telephone number, including area code)

Not Applicable (Former name or former address, if changed since last report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2. below): ☐ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425) ☐ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a- 12) ☐ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b)) ☐ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

* * * * * Securities registered pursuant to Section 12(b) of the Act:

Title of each classTrading Symbol(s)Name of exchange on which registered Class A common stock, no par valueFIBKNASDAQ

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter). Emerging growth company ☐ If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐ * * * * *

Item 2.02 Results of Operations and Financial Condition. On April 28, 2022, First Interstate BancSystem, Inc. (the “Company”) issued a press release regarding its financial results for the quarter ended March 31, 2022. A copy of the press release is furnished herewith as Exhibit 99.1 and is incorporated by reference herein. Neither the information included or incorporated by reference under this Item 2.02, nor the press release furnished herewith, shall be deemed to be “filed” for purposes of Section 18 of the Securities Exchange Act of 1934 (the “Exchange Act”) or incorporated by reference into any registration statement or other document filed pursuant to the Securities Act of 1933 (the “Securities Act”) or the Exchange Act, except as expressly set forth by specific reference in such filing.

Item 7.01 Regulation FD Disclosure. On April 28, 2022, the Company posted a new corporate presentation (the “Presentation”) on the News and Events page of the Company’s website at https://www.fibk.com. The Presentation, which is furnished with this Current Report as Exhibit 99.2 and incorporated herein by reference, updates previously furnished presentations and provides an overview of the Company and its operations. Neither the information included or incorporated by reference under this Item 7.01, nor the Presentation furnished herewith, shall be deemed to be “filed” for purposes of Section 18 of the Securities Exchange Act or incorporated by reference into any filing under the Securities Act or the Exchange Act, except as expressly set forth by specific reference in such a filing.

Item 8.01 Other Events. On April 28, 2022, the Company also announced that the Board of Directors of the Company declared, on April 27, 2022, a dividend of $0.41 per share, that is payable May 20, 2022 to shareholders of record of the Company as of May 10, 2022.

Item 9.01 Financial Statements and Exhibits.

(d)Exhibit NumberDescription

99.1 Press Release dated April 28, 2022.

99.2

Presentation

104Cover Page Interactive Data File (embedded within Inline XBRL document).

SIGNATURES

Pursuant to the requirements of the Securities and Exchange Act of 1934, the Registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized. Date: April 28, 2022

FIRST INTERSTATE BANCSYSTEM, INC.

By:/s/ KEVIN P. RILEY Kevin P. Riley President and Chief Executive Officer

fibk-20220127false000086041300008604132022-01-272022-01-27

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of report (date of earliest event reported): January 27, 2022

FIRST INTERSTATE BANCSYSTEM, INC.

(Exact name of registrant as specified in its charter)

Montana001-34653 81-0331430 (State or other jurisdiction of incorporation or organization)(Commission File No.) (IRS Employer Identification No.)

401 North 31st Street

Billings, MT 59116-0918 (Address of principal executive offices)(zip code)

(406)255-5311 (Registrant’s telephone number, including area code)

Not Applicable (Former name or former address, if changed since last report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2. below): ☒ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425) ☐ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a- 12) ☐ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b)) ☐ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

* * * * * Securities registered pursuant to Section 12(b) of the Act:

Title of each classTrading Symbol(s)Name of exchange on which registered Class A common stock, no par valueFIBKNASDAQ

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter). Emerging growth company ☐ If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐ * * * * *

Item 2.02 Results of Operations and Financial Condition. On January 27, 2022, First Interstate BancSystem, Inc. (the “Company”) issued a press release regarding its financial results for the quarter ended December 31, 2021. A copy of the press release is furnished herewith as Exhibit 99.1 and is incorporated by reference herein. Neither the information included or incorporated by reference under this Item 2.02, nor the press release furnished herewith, shall be deemed to be “filed” for purposes of Section 18 of the Securities Exchange Act of 1934 (the “Exchange Act”) or incorporated by reference into any registration statement or other document filed pursuant to the Securities Act of 1933 (the “Securities Act”) or the Exchange Act, except as expressly set forth by specific reference in such filing.

Item 7.01 Regulation FD Disclosure. On January 27, 2022, the Company posted a new corporate presentation (the “Presentation”) on the News and Events page of the Company’s website at https://www.fibk.com. The Presentation, which is furnished with this Current Report as Exhibit 99.2 and incorporated herein by reference, updates previously furnished presentations and provides an overview of the Company and its operations. Neither the information included or incorporated by reference under this Item 7.01, nor the Presentation furnished herewith, shall be deemed to be “filed” for purposes of Section 18 of the Securities Exchange Act or incorporated by reference into any filing under the Securities Act or the Exchange Act, except as expressly set forth by specific reference in such a filing.

Item 8.01 Other Events. On January 27, 2022, the Company also announced that the Board of Directors of the Company declared, on January 26, 2022, a dividend of $0.41 per share, that is payable February 21, 2022 to shareholders of record of the Company as of February 10, 2022.

Item 9.01 Financial Statements and Exhibits.

(d)Exhibit NumberDescription

99.1 Press Release dated January 27, 2021.

99.2

Presentation

104Cover Page Interactive Data File (embedded within Inline XBRL document).

SIGNATURES

Pursuant to the requirements of the Securities and Exchange Act of 1934, the Registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized. Date: January 27, 2022

FIRST INTERSTATE BANCSYSTEM, INC.

By:/s/ KEVIN P. RILEY Kevin P. Riley President and Chief Executive Officer

fibk-20211025false000086041300008604132021-10-252021-10-25

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of report (date of earliest event reported): October 25, 2021

FIRST INTERSTATE BANCSYSTEM, INC.

(Exact name of registrant as specified in its charter)

Montana001-34653 81-0331430 (State or other jurisdiction of incorporation or organization)(Commission File No.) (IRS Employer Identification No.)

401 North 31st Street

Billings, MT 59116-0918 (Address of principal executive offices)(zip code)

(406)255-5390 (Registrant’s telephone number, including area code)

Not Applicable (Former name or former address, if changed since last report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2. below): ☐ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425) ☐ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a- 12) ☐ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b)) ☐ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

* * * * * Securities registered pursuant to Section 12(b) of the Act:

Title of each classTrading Symbol(s)Name of exchange on which registered Class A common stock, no par valueFIBKNASDAQ

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter). Emerging growth company ☐ If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐ * * * * *

Item 2.02 Results of Operations and Financial Condition. On October 26, 2021, First Interstate BancSystem, Inc. (the “Company”) issued a press release regarding its financial results for the quarter ended September 30, 2021. A copy of the press release is furnished herewith as Exhibit 99.1 and is incorporated by reference herein. Neither the information included or incorporated by reference under this Item 2.02, nor the press release furnished herewith, shall be deemed to be “filed” for purposes of Section 18 of the Securities Exchange Act of 1934 (the “Exchange Act”) or incorporated by reference into any registration statement or other document filed pursuant to the Securities Act of 1933 (the “Securities Act”) or the Exchange Act, except as expressly set forth by specific reference in such filing.

Item 7.01 Regulation FD Disclosure. On October 26, 2021, the Company posted a new corporate presentation (the “Presentation”) on the News and Events page of the Company’s website at https://www.fibk.com. The Presentation, which is furnished with this Current Report as Exhibit 99.2 and incorporated herein by reference, updates previously furnished presentations and provides an overview of the Company and its operations. Neither the information included or incorporated by reference under this Item 7.01, nor the Presentation furnished herewith, shall be deemed to be “filed” for purposes of Section 18 of the Securities Exchange Act or incorporated by reference into any filing under the Securities Act or the Exchange Act, except as expressly set forth by specific reference in such a filing.

Item 8.01 Other Events. On October 26, 2021, the Company also announced that the Board of Directors of the Company declared, on October 25, 2021, a dividend of $0.41 per share, that is payable November 18, 2021 to shareholders of record of the Company as of November 8, 2021.

Item 9.01 Financial Statements and Exhibits.

(d)Exhibit NumberDescription

99.1 Press Release dated October 26, 2021.

99.2

Presentation

104Cover Page Interactive Data File (embedded within Inline XBRL document).

SIGNATURES

Pursuant to the requirements of the Securities and Exchange Act of 1934, the Registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized. Date: October 26, 2021

FIRST INTERSTATE BANCSYSTEM, INC.

By:/s/ KEVIN P. RILEY Kevin P. Riley President and Chief Executive Officer