Discover Financial Services (DFS) 10-Q 2017 Q3 Quarterly report

Exhibit 32.1

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 Discover Financial Services (the “Company”) on Form 10-Q for the period ended September 30, 2017, as filed with the Securities and Exchange Commission (the “Report”), each of David W. Nelms, Chairman of the Board and Chief Executive Officer of the Company, and R. Mark Graf, Executive Vice President and Chief Financial Officer of the Company, certifies, 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.

Date: November 2, 2017

/s/ DAVID W. NELMS

David W. Nelms

Chairman of the Board and Chief Executive Officer

Date: November 2, 2017

/s/ R. MARK GRAF

R. Mark Graf

Executive Vice President and Chief Financial Officer