UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, DC 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 23, 2013

Atlas Resource Partners, L.P.

(Exact name of registrant as specified in its chapter)

Registrant’s telephone number, including area code: 800-251-0171

(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 (see General Instruction A.2. below):

Item 1.01. Entry into a Material Definitive Agreement.

On January 23, 2013, Atlas Energy Holdings Operating Company, LLC and Atlas Resource Finance Corporation (collectively the “Issuers”), wholly-owned subsidiaries of Atlas Resource Partners, L.P. (“ARP”), completed the issuance and sale of $275 million of their 7.750% Senior Notes due 2021 (the “Notes”). The Notes were offered and sold in a private transaction under Rule 144A and Regulation S of the Securities Act of 1933, as amended, have not been registered under the Securities Act and may not be offered or sold in the United States absent registration or an exemption from the registration requirements of the Securities Act. The Notes are unconditionally guaranteed by ARP and its domestic subsidiaries (other than Atlas Energy Securities, LLC and its subsidiary) (the “Guarantors”).

The Notes were sold in accordance with the previously reported purchase agreement (the “Purchase Agreement”) dated January 16, 2013, among the Issuers, the Guarantors and the initial purchasers named therein. The Issuers issued the Notes pursuant to an indenture dated as of January 23, 2013 among the Issuers, the Guarantors and U.S. Bank National Association, as trustee (the “Indenture”).

The Issuers and the Guarantors also entered into a registration rights agreement (the “Registration Rights Agreement”) with the Initial Purchasers dated as of January 23, 2013. Under the Registration Rights Agreement, the Issuers and the Guarantors will cause to be filed with the Securities and Exchange Commission a registration statement with respect to an offer to exchange the Notes for substantially identical notes that are registered under the Securities Act. The Issuers and the Guarantors will use their reasonable best efforts to cause the exchange offer registration statement to become effective under the Securities Act. In addition, the Issuers and the Guarantors will use their reasonable best efforts to cause the exchange offer to be consummated not later than 365 days after the issuance of the Notes. Under some circumstances, in lieu of, or in addition to, a registered exchange offer, the Issuers and the Guarantors have agreed to file a shelf registration statement with respect to the Notes. The Issuers and the Guarantors are required to pay additional interest if they fail to comply with their obligations to register the Notes within the specified time periods.

This summary of the Indenture and the Registration Rights Agreement does not purport to be complete and is qualified in its entirety by reference to the agreements, copies of which are attached hereto as Exhibits 10.1 and 10.2.

Item 2.03. Creation of a Direct Financial Obligation or an Obligation under an Off-Balance Sheet Arrangement of a Registrant.

As described under Item 1.01 above, on January 23, 2013, the Issuers completed an offering of $275 million of the Notes. The Indenture governing the Notes is filed hereto as Exhibit 10.1.

Item 9.01. Financial Statements and Exhibits.

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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.

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EXHIBIT INDEX

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