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): August 1, 2013

Apco Oil and Gas International Inc.

(Exact name of registrant as specified in its charter)

(539) 573-2164

(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:

Item 7.01. Regulation FD Disclosure.

On August 1, 2013, the majority owner of Apco Oil and Gas International, Inc. (“Apco” or the “Company”), WPX Energy, Inc. (“WPX”), issued a press release announcing WPX’s financial and operational results for the three and six months ended June 30, 2013. The press release disclosed certain operational information regarding Apco. A copy of the press release is attached hereto as Exhibit 99.1 and is incorporated by reference into this Item 7.01.

WPX will host a conference call on August 1, 2013 to discuss its financial and operational results. WPX provided an electronic slide presentation on its website in connection with the conference call. Portions of that slide presentation addressed certain operational results of Apco. A copy of that slide is attached hereto as Exhibit 99.2 and is incorporated by reference into this Item 7.01.

Item 9.01. Financial Statements and Exhibits.

The information contained under Items 7.01 and 9.01 of this Current Report on Form 8-K shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended, and shall not be deemed incorporated by reference in any filing with the Securities and Exchange Commission under the Securities Exchange Act of 1934 or the Securities Act of 1933, whether made before or after the date hereof and irrespective of any general incorporation language in any filings.

Portions of this report may constitute “forward-looking statements” as defined by federal law. Although the Company believes any such statements are based on reasonable assumptions, there is no assurance that actual outcomes will not be materially different. Additional information about issues that could lead to material changes in the Company’s performance is contained in the Company’s filings with the Securities and Exchange Commission. The Company undertakes no obligation to publicly update or revise any forward-looking statements to reflect events or circumstances after the date hereof.

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.

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