6-K

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549

FORM 6-K

REPORT OF FOREIGN PRIVATE ISSUER PURSUANT TO RULE 13a-16 OR 15d-16 UNDER THE SECURITIES EXCHANGE ACT OF 1934

For the month of June, 2026

Commission File Number 001-34175

Indicate by check mark whether the registrant files or will file annual reports under cover of Form 20-F or Form 40-F.

Form 20-F x      Form 40-F ¨

Indicate by check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101(b)(1)

Yes ¨      No x

Indicate by check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101(b)(7)

Yes ¨      No x

Indicate by check mark whether the registrant by furnishing the information contained in this form is also thereby furnishing the information to the Commission pursuant to Rule 12g3-2(b) under the Securities Exchange Act of 1934.

Yes ¨      No x

If “Yes” is marked, indicate below the file number assigned to the registrant in connection with Rule 12g3-2(b): 82- N/A

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, thereunto duly authorized.

Date: June 14, 2026

Ecopetrol and the Oil Workers Union (USO) Reach FinalAgreement in Collective Bargaining Process

Bogota D.C., June 15, 2026

Ecopetrol S.A. (BVC: ECOPETROL; NYSE: EC, the “Company”) announces that, on June 13, 2026, as part of the collective bargaining process, it reached a final agreement on a new collective bargaining agreement with the Oil Workers Union (Unión Sindical Obrera – USO), the majority union and holder of the collective bargaining agreement. The new agreement has a term of six years, effective as of January 1, 2026.

In addition, in accordance with applicable law, the Company has entered into 66 final agreements with other participating labor unions.

This outcome reflects the discussions held during the direct negotiation stage and its extension, which took place over the course of more than 990 sessions in an environment grounded in dialogue, mutual respect, active listening, and collaborative engagement.

The agreements reached include improvements in working conditions, as well as enhanced benefits in health and education, the strengthening of diversity, equity, and inclusion initiatives, and social investment, among other aspects. These measures are intended to contribute to the well-being of employees and their families, strengthen relationships with key stakeholders, and align with the Company’s principles of reasonableness, efficiency, and cost discipline.

In the coming days, the Company expects to carry out the necessary procedures for the formalization and filing of the agreement with the Ministry of Labor. Subsequently, the Company and the USO negotiating teams intend to conduct joint nationwide sessions to communicate and explain the agreements reached. There can be no assurance as to the timing of such procedures or sessions.

The Company acknowledges and appreciates the work and commitment of all employees and union representatives who contributed their expertise and efforts to the successful completion of this process.

Ecopetrol is the largest company in Colombia andone of the main integrated energy companies in the American continent, with more than 19,000 employees. In Colombia, it is responsiblefor more than 60% of the hydrocarbon production of most transportation, logistics, and hydrocarbon refining systems, and it holds leadingpositions in the petrochemicals and gas distribution segments. With the acquisition of 51.4% of ISA’s shares, the company participatesin energy transmission, the management of real-time systems (XM), and the Barranquilla–Cartagena coastal highway concession. Atthe international level, Ecopetrol has a stake in strategic basins in the American continent, with drilling and exploration operationsin the United States (Permian basin and the Gulf of Mexico), Brazil, and Mexico, and, through ISA and its subsidiaries, Ecopetrol holdsleading positions in the power transmission business in Brazil, Chile, Peru, and Bolivia, road concessions in Chile, and the telecommunicationssector.

This release contains statements that may be consideredforward-looking statements within the meaning of Section 27A of the U.S. Securities Act of 1933, as amended, and Section 21E of the U.S.Securities Exchange Act of 1934, as amended. All forward-looking statements, whether made in this release or in future filings or pressreleases, or orally, address matters that involve risks and uncertainties, including in respect of the Company’s prospects forgrowth and its ongoing access to capital to fund the Company’s business plan, among others. Consequently, changes in the followingfactors, among others, could cause actual results to differ materially from those included in the forward-looking statements: marketprices of oil & gas, our exploration, and production activities, market conditions, applicable regulations, the exchange rate, theCompany’s competitiveness and the performance of Colombia’s economy and industry, to mention a few. We do not intend anddo not assume any obligation to update these forward-looking statements. ****

For more information, please contact:

Investor Relations Office

Email: [email protected]

Head of Corporate Communications (Colombia)

Marcela Ulloa

Email: [email protected]