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 10, 2014

PANHANDLE EASTERN PIPE LINE COMPANY, LP

(Exact name of Registrant as specified in its charter)

3738 Oak Lawn Avenue

Dallas, TX 75219

(Address of principal executive offices, including zip code)

(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 1.01. Entry into a Material Definitive Agreement.

On January 10, 2014, Panhandle Eastern Pipe Line Company, LP (the “Partnership”) entered into an Agreement and Plan of Merger (the “Merger Agreement”) with Southern Union Company, a Delaware corporation and the indirect parent of the Partnership (“Southern Union”), and PEPL Holdings, LLC, a Delaware limited liability company and the sole limited partner of the Partnership (“PEPL Holdings”), pursuant to which each of Southern Union and PEPL Holdings were merged with and into the Partnership (the “Merger”), with the Partnership surviving the Merger.

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

In connection with the consummation of the Merger, on January 10, 2014, the Partnership, Southern Union and The Bank of New York Mellon Trust Company, N.A. (formerly known as The Bank of New York Trust Company, N.A.) (“BNY Mellon”) entered into (i) Supplemental Indenture No. 5 (“Supplemental Indenture No. 5”) to the Indenture, dated as of January 31, 1994, between Southern Union and BNY Mellon, as trustee, as supplemented by the Officers’ Certificate, dated January 31, 1994, the Officers’ Certificate, dated November 3, 1999, the Supplemental Indenture No. 3, dated as of June 24, 2013, and the Supplemental Indenture No. 4, dated as of June 24, 2013 (as so supplemented and amended, the “Senior Indenture”), and (ii) the Fourth Supplemental Indenture (“Fourth Supplemental Indenture” and, together with Supplemental Indenture No. 5, the “Supplemental Indentures”) to the Indenture, dated as of May 10, 1995, between Southern Union and BNY Mellon, as trustee, as supplemented by the First Supplemental Indenture, dated as of May 10, 1995, the Second Supplemental Indenture, dated as of October 23, 2006, and the Third Supplemental Indenture, dated as of June 24, 2013 (as so supplemented and amended, the “Junior Indenture” and, together with the Senior Indenture, the “Southern Union Indentures”). Pursuant to the Supplemental Indentures, the Partnership assumed Southern Union’s obligations under its 7.60% Senior Notes due 2024 (the “2024 Notes”), 8.25% Senior Notes due 2029 (the “2029 Notes” and, together with the 2024 Notes, the “Senior Notes”) and Floating Rate Junior Subordinated Notes due 2066 (the “Junior Notes” and, together with the Senior Notes, the “Southern Union Notes”).

There is currently outstanding $82,514,000 in aggregate principal amount of the 2024 Notes, $33,325,000 in aggregate principal amount of the 2029 Notes and $54,469,000 in aggregate principal amount of the Junior Notes. The Southern Union Notes will be the Partnership’s unsecured and unsubordinated obligations, ranking equally in right of payment with the Partnership’s existing and future unsubordinated debt.

Interest on the 2024 Notes is payable semi-annually on February 1 and August 1, while interest on the 2029 Notes is payable semi-annually on May 15 and November 15. Subject to the Partnership’s right to defer interest payments on the Junior Notes on one or more occasions for up to 10 consecutive years, interest on the Junior Notes is payable quarterly. Beginning on November 1, 2011, the interest rate is a floating rate based on three-month LIBOR plus 301.75 basis points, and is reset quarterly. Any deferred interest payments will accumulate additional interest at a rate equal to the interest rate then applicable to the Junior Notes, to the extent permitted by law. The Partnership may redeem the Junior Notes, in whole or in part, at any time at par, plus accrued and unpaid interest, if any, to the redemption date.

The foregoing description of the Southern Union Notes, the Southern Union Indentures and the Supplemental Indentures does not purport to be complete and is subject to, and qualified in its entirety by, the full text of the Southern Union Indentures and Supplemental Indentures, which are included as Exhibits 4.1 through 4.10 hereto.

Item 5.03. Amendments to Articles of Incorporation or Bylaws; Change in Fiscal Year.

On January 10, 2014, the sole general partner and sole limited partner of the Partnership adopted Amendment No. 1 (the “LP Agreement Amendment”) to the Agreement of Limited Partnership of the Partnership, dated as of June 29, 2004, to reflect the ownership in the Partnership following the Merger.

The above description of the LP Agreement Amendment does not purport to be complete and is subject to, and qualified in its entirety by, the full text of the LP Agreement Amendment, which is attached as Exhibit 3.1 hereto.

Item 9.01. Financial Statements and 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 hereunto duly authorized.

EXHIBIT INDEX