Columbia Banking System (COLB) 10-Q 2020 Q3 Quarterly report

EXHIBIT 32

CERTIFICATION PURSUANT TO

18 U.S.C. SECTION 1350,

AS ADOPTED PURSUANT TO

SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002

In connection with the Quarterly Report of Columbia Banking System, Inc. (the “Company”) on Form 10-Q for the period ended September 30, 2020 as filed with the Securities and Exchange Commission on the date hereof (the “Report”), we, Clint E. Stein, President and Chief Executive Officer, and Aaron J. Deer, Executive Vice President and Chief Financial Officer, certify, pursuant to 18 U.S.C. Section 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, that:

(1)The Report fully complies with the requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934; and

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

/s/ CLINT E. STEIN

Clint E. Stein
President and
Chief Executive Officer
Columbia Banking System, Inc.

/s/ AARON JAMES DEER

Aaron James Deer
Executive Vice President and
Chief Financial Officer
Columbia Banking System, Inc.

Dated: November 5, 2020