Exhibit 24
POWER OF ATTORNEY

     Know all by these presents that the undersigned hereby constitutes and
appoints each of Philip Castrogiovanni, Efie Vainikos, and Michael Ebner,
signing singly, the undersigned's true and lawful attorney-in-fact to:

          (1) execute for and on behalf of the undersigned, all reports to be
filed by the undersigned pursuant to Section 16(a) of the Securities Exchange
Act of 1934, as amended (the "Exchange Act"), and the rules promulgated
thereunder (including Forms 3, 4 and 5, and any successor forms) (the "Section
16 Reports") with respect to the equity securities of Discover Financial
Services (the "Company"); and

          (2) do and perform any and all acts for and on behalf of the
undersigned that may be necessary or desirable to complete and execute any such
Section 16 Reports, complete and execute any amendment or amendments thereto,
and file such report with the U.S. Securities and Exchange Commission and any
stock exchange or similar authority; and

          (3) take any other action of any type whatsoever in connection with
the foregoing that, in the opinion of such attorney-in-fact, may be of benefit
to, in the best interest of, or legally required by, the undersigned, it being
understood that the documents executed by such attorney-in-fact on behalf of the
undersigned pursuant to this Power of Attorney shall be in such form and shall
contain such terms and conditions as such attorney-in-fact may approve in such
attorney-in-fact's discretion.

     The powers granted above may be exercised by each such attorney-in-fact on
behalf of the undersigned, individually, and on behalf of the undersigned in any
fiduciary or representative capacity in which the undersigned may be acting.

     The undersigned hereby grants to each such attorney-in-fact full power and
authority to do and perform any and every act and thing whatsoever requisite,
necessary, or proper to be done in the exercise of any of the rights and powers
herein granted, as fully to all intents and purposes as the undersigned might or
could do if personally present, with full power of substitution or revocation,
hereby ratifying and confirming all that such attorney-in-fact, or such
attorney-in-fact's substitute or substitutes, shall lawfully do or cause to be
done by virtue of this Power of Attorney and the rights and powers herein
granted.  The undersigned acknowledges that the foregoing attorneys-in-fact, in
serving in such capacity at the request of the undersigned, are not assuming,
nor is the Company assuming, any of the undersigned's responsibilities to comply
with Section 16 of the Exchange Act.

     This Power of Attorney shall be effective as of the date set forth below
and shall continue in full force and effect until the undersigned is no longer
required to file Section 16 Reports with respect to the equity securities of the
Company, unless earlier (a) revoked by the undersigned in a signed writing
delivered to the foregoing attorneys-in-fact or (b) superseded by a new power of
attorney regarding the purposes outlined herein as of a later date.

     IN WITNESS WHEREOF, the undersigned has caused this Power of Attorney to be
executed as of this 22nd day of February, 2023.

Signature: /s/ Candace H. Duncan
Print Name: Candace H. Duncan