UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d)

of the Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): August 14, 2015

51-0020270

(IRS Employer Identification No. of the sponsor and depositor)

(302) 323-7315

(Telephone Number, including area code)

Former name or former address, if changed since last report: Not Applicable

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

Class B(2015-1) Notes. On August 14, 2015, Discover Card Execution Note Trust entered into the Class B(2015-1) Terms Document, dated as of August 14, 2015, between Discover Card Execution Note Trust, as Issuer, and U.S. Bank National Association, as Indenture Trustee.

Unregistered Sale of Class B(2015-1) Notes and Class C(2015-1) Notes. On August 14, 2015, Discover Card Execution Note Trust sold $450,000,000 principal amount of the DiscoverSeries Class B(2015-1) Notes (the “Notes”) in reliance upon the exemption contained in Section 4(a)(2) of the Securities Act of 1933, as amended. The Notes were sold at a discount for $440,550,450, with no applicable underwriting discounts or commissions, and will not bear interest prior to their expected maturity. In connection with this issuance, the investor interest in receivables represented by the collateral certificate issued by the Discover Card Master Trust I that secures the DiscoverSeries Notes was increased by $450,000,000. Discover Card Execution Note Trust paid the net proceeds from the issuance to Discover Bank in exchange for the increase in the investor interest in receivables represented by the collateral certificate.

Increase in Principal Amount of Class D(2009-1) Notes. On August 14, 2015, Discover Bank, pursuant to Section 2.03 of the Note Purchase Agreement (the “Note Purchase Agreement”), dated as of July 2, 2009, among Discover Card Execution Note Trust, as Issuer, Discover Bank, as Depositor, and the purchasers named therein and Section 2.06 of the Class D(2009-1) Terms Document, dated as of July 2, 2009, as the same may be further amended, supplemented, restated, amended and restated, replaced or otherwise modified from time to time, by and between Discover Card Execution Note Trust, as Issuer, and U.S. Bank National Association as Indenture Trustee, increased the Outstanding Dollar Principal Amount of the Class D(2009-1) Notes. The increase in the Outstanding Dollar Principal Amount of the Class D(2009-1) Notes was in the amount of $61,363,636, resulting in an Outstanding Dollar Principal Amount of the Class D(2009-1) Notes of $2,574,545,455. The Class D(2009-1) Notes were sold to purchasers in reliance upon the exemption contained in Section 4(a)(2) of the Securities Act of 1933, as amended. The Notes were sold at par value for cash, with no applicable underwriting discounts or commissions. In connection with this increase, the investor interest in receivables represented by the collateral certificate issued by the Discover Card Master Trust I that secures the DiscoverSeries Notes was increased by $61,363,636. Discover Card Execution Note Trust paid the net proceeds from the issuance to Discover Bank in exchange for the increase in the investor interest in receivables represented by the collateral certificate.

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the Registrant has duly caused this report to be signed on its behalf by the undersigned thereunto duly authorized.

Date: August 14, 2015

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