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

June 18, 2012

Date of Report (Date of earliest event reported)

ENERGY TRANSFER PARTNERS, L.P.

(Exact name of Registrant as specified in its charter)

3738 Oak Lawn Avenue

Dallas, TX 75219

(Address of principal executive offices)

(214) 981-0700

(Registrant’s 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 7.01. Regulation FD Disclosure.

On June 18, 2012, Energy Transfer Partners, L.P. (“ETP”) and Energy Transfer Equity, L.P. (“ETE”) issued a joint press release announcing that ETE plans to drop down its interest in Southern Union Company (“SUG”) into an ETP-controlled entity, which will also include assets to be acquired in the recently announced merger between Sunoco, Inc. (“Sunoco”) and ETP.

Concurrent with the closing of the Sunoco merger, ETE will contribute its interest in SUG into an ETP-controlled entity in exchange for a sixty percent (60%) equity interest in a newly formed entity, ETP Holdco Corporation (“HoldCo”). In conjunction with ETE’s contribution, ETP will contribute its interest in Sunoco to HoldCo and will retain a forty percent (40%) equity interest in HoldCo. Prior to the contribution of Sunoco to HoldCo, Sunoco’s interests in Sunoco Logistics Partners L.P. (“SXL”) will be transferred to ETP.

Copies of the joint press release and an informational presentation regarding the transactions discussed hereunder are furnished herewith as Exhibit 99.1 and Exhibit 99.2, respectively, and are incorporated herein by reference.

In accordance with General Instruction B.2 of Form 8-K, the information set forth in this Item 7.01 and in the attached Exhibits 99.1 and Exhibit 99.2 is deemed to be “furnished” and shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended.

Item 8.01. Other Events.

To the extent required, the information included in Item 7.01 of this Form 8-K is incorporated into this item 8.01.

Item 9.01. Financial Statements and Exhibits.

(d) Exhibits.

IMPORTANT ADDITIONAL INFORMATION WILL BE FILED WITH THE SEC

In connection with the proposed business combination transaction between ETP and Sunoco, ETP plans to file with the U.S. Securities and Exchange Commission (the “SEC”) a registration statement on Form S-4 that will contain a proxy statement/prospectus to be mailed to the Sunoco shareholders in connection with the proposed transaction. THE REGISTRATION STATEMENT AND THE PROXY STATEMENT/PROSPECTUS WILL CONTAIN IMPORTANT INFORMATION ABOUT ETP, ETE, SUNOCO, THE PROPOSED TRANSACTION AND RELATED MATTERS. INVESTORS AND SECURITY HOLDERS ARE URGED TO READ THE REGISTRATION STATEMENT AND THE PROXY/PROSPECTUS CAREFULLY WHEN THEY BECOME AVAILABLE. Investors and security holders will be able to obtain free copies of the registration statement and the proxy statement/prospectus and other documents filed with the SEC by ETP and Sunoco through the web site maintained by the SEC at www.sec.gov. In addition, investors and security holders will be able to obtain free copies of the registration statement and the proxy statement/prospectus by phone, e-mail or written request by contacting the investor relations department of ETP or Sunoco at the following:

PARTICIPANTS IN THE SOLICITATION

ETE, ETP and Sunoco, and their respective directors and executive officers, may be deemed to be participants in the solicitation of proxies in respect of the proposed transactions contemplated by the Sunoco merger agreement previously filed by ETP. Information regarding directors and executive officers of ETP’s general partner is contained in ETP’s Form 10-K for the year ended December 31, 2011, which has been filed with the SEC. Information regarding directors and executive officers of ETP’s general partner is contained in ETP’s Form 10-K for the year ended December 31, 2011, which has been filed with the SEC. Information regarding Sunoco’s directors and executive officers is contained in Sunoco’s definitive proxy statement dated March 16, 2012, which is filed with the SEC. A more complete description will be available in the registration statement and the proxy statement/prospectus.

SAFE HARBOR FOR FORWARD-LOOKING STATEMENTS

Statements in this document regarding the proposed transaction between ETP and Sunoco, the expected timetable for completing the proposed transaction, future financial and operating results, benefits and synergies of the proposed transaction, future opportunities for the combined company, and any other statements about ETP, ETE, SXL or Sunoco managements’ future expectations, beliefs, goals, plans or prospects constitute forward looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. Any statements that are not statements of historical fact (including statements containing the words “believes,” “plans,” “anticipates,” “expects,” estimates and similar expressions) should also be considered to be forward looking statements. There are a number of important factors that could cause actual results or events to differ materially from those indicated by such forward looking statements, including: the ability to consummate the proposed transaction; the ability to obtain the requisite regulatory approvals, Sunoco shareholder approval and the satisfaction of other conditions to consummation of the transaction; the ability of ETP to successfully integrate Sunoco’s operations and employees; the ability to realize anticipated synergies and cost savings; the potential impact of announcement of the transaction or consummation of the transaction on relationships, including with employees, suppliers, customers and competitors; the ability to achieve revenue growth; national, international, regional and local economic, competitive and regulatory conditions and developments; technological developments; capital and credit markets conditions; inflation rates; interest rates; the political and economic stability of oil producing nations; energy markets, including changes in the price of certain commodities; weather conditions; environmental conditions; business and regulatory or legal decisions; the pace of deregulation of retail natural gas and electricity and certain agricultural products; the timing and success of business development efforts; terrorism; and the other factors described in the Annual Reports on Form 10-K for the year ended December 31, 2011 filed with the SEC by ETP, ETE, SXL and Sunoco. ETP, ETE, SXL and Sunoco disclaim any intention or obligation to update any forward looking statements as a result of developments occurring after the date of this document.

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 hereunto duly authorized.

Exhibit Index