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): December 11, 2015

TARGA RESOURCES PARTNERS LP

(Exact name of registrant as specified in its charter)

1000 Louisiana, Suite 4300

Houston, TX 77002

(Address of principal executive office and Zip Code)

(713) 584-1000

(Registrants’ telephone number, including area code)

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 1.01 Entry into a Material Definitive Agreement.

On December 11, 2015, Targa Resources Partners LP (the “Partnership”) and Targa Receivables LLC, a bankruptcy-remote special purpose entity that is an indirect wholly-owned subsidiary of the Partnership (the “SPV”), entered into a Fourth Amendment (the “Purchase Agreement Amendment”) to the Receivables Purchase Agreement (the “Purchase Agreement”) among the SPV, as seller, the Partnership, as servicer, the conduit purchasers, the committed purchasers, the purchaser agents and the LC participants party thereto and PNC Bank, National Association, as administrator and LC Bank, which amends the $200 million accounts receivable securitization facility (the “Facility”) by, among other things, (i) extending the Facility Termination Date (as defined in the Purchase Agreement Amendment) of the Facility to December 9, 2016, (ii) increasing the Purchase Limit (as defined in the Purchase Agreement) of the Facility to $225 million and (iii) adding Targa Midstream Services LLC, an indirect wholly-owned subsidiary of the Partnership, as an additional Originator (as defined in the Purchase Agreement). As of December 11, 2015, after giving effect to the Purchase Agreement Amendment, there were $182.1 million of trade receivable purchases outstanding under the Facility. A copy of the Purchase Agreement Amendment is filed as Exhibit 10.1 to this Current Report on Form 8-K.

The foregoing description of the Purchase Agreement Amendment does not purport to be complete and is qualified in its entirety by reference to the full text of the Purchase Agreement Amendment, which is incorporated by reference herein.

Item 9.01 Financial Statements and Exhibits.

(d) Exhibits.

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.

INDEX TO EXHIBITS