Slack (WORK) 10-Q 2021 Q2 Quarterly report

Exhibit 32.1

CERTIFICATION OF CHIEF EXECUTIVE OFFICER AND CHIEF FINANCIAL OFFICER

PURSUANT TO 18 U.S.C. SECTION 1350,

AS ADOPTED PURSUANT TO

SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002

Pursuant to the requirement set forth in Rule 13a-14(b) of the Securities Exchange Act of 1934, as amended, (the “Exchange Act”) and Section 1350 of Chapter 63 of Title 18 of the United States Code (18 U.S.C. §1350), Stewart Butterfield, Chief Executive Officer of Slack Technologies, Inc. (the “Company”), and Allen Shim, Chief Financial Officer of the Company, each hereby certifies that, to the best of his knowledge:

1.The Company’s Quarterly Report on Form 10-Q for the quarterly period ended July 31, 2020, to which this Certification is attached as Exhibit 32.1 (the “Periodic Report”), fully complies with the requirements of Section 13(a) or Section 15(d) of the Exchange Act; and

2.The information contained in the Periodic Report fairly presents, in all material respects, the financial condition and results of operations of the Company.

Date: September 8, 2020

/s/ Stewart Butterfield

Stewart Butterfield

Chief Executive Officer

(Principal Executive Officer)

/s/ Allen Shim

Allen Shim

Chief Financial Officer

(Principal Financial Officer)