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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): March 3, 2026

GRAN TIERRA ENERGY INC.

(Exact name of Registrant as specified in its charter)

Delaware98-0479924 (State or other jurisdiction of incorporation)(I.R.S. Employer Identification No.)

Commission file number: 001-34018

500 Centre Street S.E. Calgary, Alberta, Canada T2G 1A6 (Address of principal executive offices and zip code)

Registrant's telephone number, including area code: (403) 265-3221

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 class Trading Symbol(s) Name of each exchange on which registered

Common Stock, par value $0.001 per share GTE NYSE American

Toronto Stock Exchange

London Stock Exchange

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 March 3, 2026, Gran Tierra Energy Inc. issued a press release announcing its financial and operating results for the year-end December 31, 2025. A copy of the press release is attached hereto as Exhibit 99.1 and incorporated by reference herein in its entirety.

The information in this Item 2.02 and in Exhibit 99.1 attached to this report is being furnished and shall not be deemed “filed” for the purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or otherwise subject to the liabilities of that section, nor shall it be deemed to be incorporated by reference into any filing by Gran Tierra Energy Inc. under the Securities Act of 1933, as amended or the Exchange Act, regardless of any general incorporation language contained in such filing.

Item 9.01. Financial Statements and Exhibits.

(d) Exhibits

Exhibit Number Description

99.1Press Release issued on March 3, 2026, announcing financial results of Gran Tierra Energy Inc. for the year ended December 31, 2025.

104Cover Page Interactive Data File - the cover page XBRL tags are embedded within the Inline XBRL document.

SIGNATURE

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.

March 3, 2026GRAN TIERRA ENERGY INC.

By:/s/ Ryan Ellson By: Ryan Ellson Chief Financial Officer and Executive Vice President, Finance

false 0001273441

0001273441

2026-01-28 2026-01-28

iso4217:USD

xbrli:shares

iso4217:USD

xbrli:shares

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

GRAN TIERRA ENERGY INC.

(Exact Name of Registrant as Specified in its Charter)

Delaware

001-34018

98-0479924

(State or Other Jurisdiction of Incorporation)

(Commission File Number)

(IRS Employer Identification No.)

500 Centre Street S.E.

Calgary, Alberta, Canada

T2G 1A6

(Address of Principal Executive Offices)

(Zip Code)

(403) 265-3221

(Registrant’s Telephone Number, Including Area Code)

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:

¨ 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 class Trading Symbol(s) Name of each exchange on which registered

Common Stock, par value $0.001 per share GTE

NYSE American

Toronto Stock Exchange

London Stock Exchange

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, Gran Tierra Energy Inc. (the “Company”) issued a press release announcing its 2026 year-end reserves. A copy of the press release is attached hereto as Exhibit 99.1 and incorporated by reference herein in its entirety.

The disclosures set forth in Item 8.01 are incorporated by reference into this Item 2.02.

The information in this Item 2.02 and in Exhibit 99.1 attached to this Current Report on Form 8-K is being furnished and shall not be deemed “filed” for the purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or otherwise subject to the liabilities of that section, nor shall it be deemed to be incorporated by reference into any filing by the Company under the Securities Act of 1933, as amended, or the Exchange Act, regardless of any general incorporation language contained in such filing.

Item 8.01.Other Events.

The Company is hereby presenting information regarding its oil and natural gas reserves at December 31, 2025 and certain operational updates regarding the fourth quarter and the year ended December 31, 2025.

Reserves Information

Gran Tierra’s 2025 reserves were independently prepared by McDaniel.

See “Glossary” for definitions of industry terms and abbreviations. All dollar amounts are presented in U.S. dollars.

The following table sets forth Gran Tierra’s estimated reserves NAR as of December 31, 2025.

Oil Natural Gas NGL + Condensate Oil Equivalent

Reserves Category (Mbbl) (MMcf) (Mbbl)

(MBOE)

Proved

Total proved developed producing reserves 38,811 77,866 9,213 61,002

Total proved developed non-producing reserves

1,664 2,912 209 2,358

Total proved undeveloped reserves 38,824 38,243 3,061 48,259

Total proved reserves 79,299 119,021 12,483 111,619

Probable

Total probable developed producing reserves 11,182 23,413 2,703 17,787

Total probable developed non-producing reserves

510 4,134 361 1,560

Total probable undeveloped reserves 42,241 121,682 12,136 74,657

Total probable reserves 53,933 149,229 15,200 94,005

Possible

Total possible developed producing reserves 10,205 27,479 3,163 17,948

Total possible developed non-producing reserves

387 1,727 142 817

Total possible undeveloped reserves 27,461 39,664 3,470 37,542

Total possible reserves 38,053 68,870 6,775 56,306

The product prices that were used to determine the future gross revenue for each property reflect adjustments to the benchmark prices for gravity, quality, local conditions and/or distance from market. The average realized prices for reserves in the report are:

Oil (USD/bbl) – Colombia $57.32

Oil (USD/bbl) – Ecuador $63.05

Oil (USD/bbl) – Canada $56.77

Operations Update

The following table sets forth select estimated operational data for Gran Tierra for the year ended December 31, 2025.

Year Ended December 31,

2025 % Change 2024 % C