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, 2015 (January 26, 2015)

Apco Oil and Gas International Inc.

(Exact name of Registrant as Specified in its Charter)

Registrant’s Telephone Number, Including Area Code: (539) 573-2164

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:

Item 5.07 Submission of Matters to a Vote of Security Holders.

On January 26, 2015, Apco Oil and Gas International Inc., a Cayman Islands exempted company limited by shares (“Apco” or the “Company”) held an extraordinary general meeting of its shareholders (the “Extraordinary General Meeting”).

The purpose of the Extraordinary General Meeting was for the shareholders to consider and vote upon the following proposals: (1) the adoption of the Agreement and Plan of Merger (the “Merger Agreement”), dated as of October 2, 2014, by and among the Company, Pluspetrol Resources Corporation (“Parent”) and Pluspetrol Black River Corporation, a wholly-owned subsidiary of Parent (“Merger Sub”) (and the plan of merger exhibited thereto) and (2) the approval, on a non-binding advisory basis, of “golden parachute” compensation that certain executive officers of the Company will or may receive in connection with the Merger. Each of the proposals is described in the Company’s Definitive Proxy Statement on Schedule 14A filed with the Securities and Exchange Commission on December 22, 2014 (the “Proxy Statement”).

Proposal 1: Adoption of the Merger Agreement (and the plan of merger exhibited thereto).

The shareholders adopted the Merger Agreement (and the plan of merger exhibited thereto).

Proposal 2: Advisory Vote Relating to Merger-Related Compensation

The shareholders approved, on a non-binding, advisory basis, “golden parachute” compensation that certain executive officers of the Company will or may receive in connection with the Merger as disclosed in the Proxy Statement.

Item 8.01. Other Events.

On January 26, 2015, the Company issued a press release announcing the results of the Extraordinary General Meeting, a copy of which is attached hereto as Exhibit 99.1 and incorporated herein by reference.

Item 9.01. Financial Statements and Exhibits.

(d) Exhibits. The following exhibits are furnished with this Form 8-K.

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 thereunto duly authorized.

EXHIBIT INDEX