6-K

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 6-K

REPORT OF FOREIGN PRIVATE ISSUER

PURSUANT TO RULE 13a-16 OR 15d-16

OF THE SECURITIES EXCHANGE ACT OF 1934

For the month of May2026

Commission File Number: 001-39240

GFL Environmental Inc.

(Translation of registrant’s name intoEnglish)

1759 Purdy Avenue, Suite 300

Miami Beach, Florida33139

(Address of principal executive offices)

Indicate by check mark whether the registrant files or will file annual reports under cover of Form 20-F or Form 40-F.

Form 20-F ¨              Form 40-F x

Indicate by check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101(b)(1):  ¨

Indicate by check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101(b)(7):  ¨

EXHIBIT INDEX

The following Exhibits 99.1 and 99.2 are furnished as part of this Current Report on Form 6-K.

SIGNATURE

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.

Exhibit 99.1

GFL Environmental Inc. Announces Results fromAnnual and Special Meeting of Shareholders

MIAMI BEACH, FL, May 13, 2026 – GFL Environmental Inc. (NYSE: GFL) (TSX: GFL) (“GFL” or the “Company”) announced the voting results from its annual and special meeting of shareholders held today virtually via live audio webcast.

Shareholders of the Company voted in favour of all items of business, including the election of each of the director nominees as follows:

Final voting results on all matters voted on at the meeting will be filed on SEDAR+ at www.sedarplus.ca and on EDGAR at www.sec.gov.

About GFL

GFL is the fourth largest diversified environmental services company in North America, providing comprehensive solid waste management services from its platform of facilities throughout Canada and 18 U.S. states. GFL has a workforce of more than 15,000 employees across its organization.

For more information:

Patrick Dovigi

+1 905 326-0101

pdovigi@gflenv.com

Exhibit 99.2

REPORT OF VOTING RESULTS

In accordance with Section 11.3 of NationalInstrument 51-102 – Continuous Disclosure Obligations, the following sets out the matters voted upon at the annual and special meeting of shareholders (the “Meeting”) of GFL Environmental Inc. (the “Company”) held on May 13, 2026. Each of the matters set out below is described in greater detail in the Company’s management information circular dated March 31, 2026 (the “Circular”).

Each of the eight nominees listed in the Circular was elected as a director of the Company to hold office until the close of the next annual meeting of shareholders or until their successor is elected or appointed. The results of the votes cast are set out below:

KPMG LLP was appointed as the auditor of the Company until the next annual meeting of shareholders or until a successor auditor is appointed and the board of directors of the Company was authorized to fix the remuneration of the auditor. The results of the votes cast are set out below:

The resolution regarding the renewal of the Company’s Omnibus Long-Term Incentive Plan and the approval of all unallocated options, rights or other entitlements thereunder were approved. The results of the votes cast are set out below:

The resolution regarding the renewal of the Company’s Director DSU Plan and the approval of all unallocated deferred share units thereunder were approved. The results of the votes cast are set out below:

The advisory non-binding resolution on the Company’s approach to executive compensation was approved. The results of the votes cast are set out below: