Report of Foreign Issuer (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 December, 2016

Commission File Number 001-35052

Adecoagro S.A.

(Translation of registrant’s name into English)

Vertigo Naos Building, 6, Rue Eugène Ruppert, L-2453, Luxembourg

R.C.S. Luxembourg B 153 681

(Address of principal executive office)

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): ¨

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): ¨

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- .

EXPLANATORY NOTE

This Report of Foreign Private Issuer on Form 6-K (this “Form 6-K”) is being filed by Adecoagro S.A. (“Adecoagro” or the “Company”) with the Securities and Exchange Commission (the “SEC”) and is incorporated by reference into the Company’s Registration Statement on Form F-3 filed with the SEC on December 6, 2013 (File No. 333-191325) and will be deemed to be a part thereof from the date on which this Form 6-K is filed with the SEC, to the extent not superseded by documents or reports subsequently filed or furnished. This Form 6-K contains, as Exhibit 99.1, Operating and Financial Review and Prospects, which reviews Adecoagro’s results of operations and financial condition as of September 30, 2016, and for the nine-month periods ended, September 30, 2016 and 2015 . This report also incorporates by reference the Company’s annual report on Form 20-F filed with the SEC on April 27, 2016 (our “Form 20-F”).

Forward Looking Statements

This report contains forward-looking statements. The registrant desires to qualify for the “safe-harbor” provisions of the Private Securities Litigation Reform Act of 1995, and consequently is hereby filing cautionary statements identifying important factors that could cause the registrant’s actual results to differ materially from those set forth herein and in the attached Condensed Audited Financial Statements.

The registrant’s forward-looking statements are based on the registrant’s current expectations, assumptions, estimates and projections about the registrant and its industry. These forward-looking statements can be identified by words or phrases such as “anticipate,” “believe,” “continue,” “estimate,” “expect,” “intend,” “is/are likely to,” “may,” “plan,” “should,” “would,” or other similar expressions.

The forward-looking statements included in the attached relate to, among others: (i) the registrant’s business prospects and future results of operations; (ii) weather and other natural phenomena; (iii) developments in, or changes to, the laws, regulations and governmental policies governing the registrant’s business, including limitations on ownership of farmland by foreign entities in certain jurisdictions in which the registrant operate, environmental laws and regulations; (iv) the implementation of the registrant’s business strategy; (v) the registrant’s plans relating to acquisitions, joint ventures, strategic alliances or divestitures; (vi) the implementation of the registrant’s financing strategy and capital expenditure plan; (vii) the maintenance of the registrant’s relationships with customers; (viii) the competitive nature of the industries in which the registrant operates; (ix) the cost and availability of financing; (x) future demand for the commodities the registrant produces; (xi) international prices for commodities; (xii) the condition of the registrant’s land holdings; (xiii) the development of the logistics and infrastructure for transportation of the registrant’s products in the countries where it operates; (xiv) the performance of the South American and world economies; and (xv) the relative value of the Brazilian Real, the Argentine Peso, and the Uruguayan Peso compared to other currencies; as well as other risks included in the registrant’s other filings and submissions with the United States Securities and Exchange Commission.

These forward-looking statements involve various risks and uncertainties. Although the registrant believes that its expectations expressed in these forward-looking statements are reasonable, its expectations may turn out to be incorrect. The registrant’s actual results could be materially different from its expectations. In light of the risks and uncertainties described above, the estimates and forward-looking statements discussed in the attached might not occur, and the registrant’s future results and its performance may differ materially from those expressed in these forward-looking statements due to, inclusive, but not limited to, the factors mentioned above. Because of these uncertainties, you should not make any investment decision based on these estimates and forward-looking statements.

The forward-looking statements made in the attached relate only to events or information as of the date on which the statements are made in the attached. The registrant undertakes no obligation to update any forward-looking statements to reflect events or circumstances after the date on which the statements are made or to reflect the occurrence of unanticipated events.

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.