Donnelley Financial Solutions (DFIN) 10-Q 2023 Q1 Quarterly report

Exhibit 32.1

CERTIFICATION OF CHIEF EXECUTIVE OFFICER

CERTIFICATION PURSUANT TO RULE 13a-14(b) OR RULE 15d-14(b)

AND SECTION 1350 OF CHAPTER 63 OF TITLE 18

OF THE UNITED STATES CODE (18 U.S.C. 1350),

AS ADOPTED PURSUANT TO

SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002

In connection with the Quarterly Report of Donnelley Financial Solutions, Inc. (the “Company”) on Form 10-Q for the period ending March 31, 2023 as filed with the Securities and Exchange Commission on the date hereof (the “Report”), I, Daniel N. Leib, President and Chief Executive Officer of the Company, certify, pursuant to 18 U.S.C. § 1350, as adopted pursuant to § 906 of the Sarbanes-Oxley Act of 2002, that to the best of my knowledge:

(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.

Date: May 3, 2023

/s/ DANIEL N. LEIB

Daniel N. Leib

President and Chief Executive Officer