PLAINS ALL AMERICAN PIPELINE LP

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) — September 8, 2026

Plains All American Pipeline, L.P.

(Exact name of registrant as specified in its charter)

333 Clay Street, Suite 1600, Houston, Texas 77002

(Address of principal executive offices) (Zip Code)

713-646-4100

(Registrant’s telephone number, including area code)

(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:

Securities registered pursuant to Section 12(b) of the Act:

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter).

Emerging growth company  ¨

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act.  ¨

Item 2.02. Results of Operations and Financial Condition.

Plains All American Pipeline, L.P. (“PAA”) is providing an unaudited pro forma condensed statement of combined operations of PAA for the year ended December 31, 2025 (the “pro forma statement of operations”), as described in Item 8.01 below and which is incorporated into this Item 2.02 by reference. The pro forma statement of operations gives effect to (1) the purchase completed on October 1, 2025 of an aggregate 55% non-operated equity interest in EPIC Crude Holdings, LP (“EPIC Crude Holdings”), the entity that owned and operated the Cactus III Pipeline (formerly known as the EPIC Crude Oil Pipeline), and an aggregate 55% of the membership interests in EPIC Crude Holdings GP, LLC (“EPIC GP”), the general partner of EPIC Crude Holdings (the “EPIC 55% Transaction”) and (2) the purchase effective November 1, 2025 of the remaining 45% equity interest in EPIC Crude Holdings and the remaining 45% of the membership interests in EPIC GP (the “EPIC 45% Transaction,” and, together with the EPIC 55% Transaction, the “Transactions”), as if such Transactions had been consummated on January 1, 2025.

Item 8.01. Other Events.

Pro Forma Financials

The following pro forma financial information, which gives effect to the Transactions as if they had been consummated on January 1, 2025, is provided in Exhibit 99.1 attached hereto:

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 hereunto duly authorized.