UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, DC 20549

FORM 8-K /A

CURRENT REPORT

Pursuant to Section 13 or 15(d) of the

Securities Exchange Act of 1934

June 18, 2012

Date of Report (Date of earliest event reported)

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

Explanatory Statement

On June 18, 2012, Exelon Corporation (Exelon) and Exelon Generation Company, LLC (Generation) filed a Current Report on Form 8-K to report the sale of two tranches of Senior Notes by Generation (the “Original Report”). Exelon and Generation are filing this Form 8-K/A as an amendment to the Original Report to correct Item 1.01 and Item 2.03 of the Original Report which contained two typographical errors regarding the Senior Notes. The Original Report stated that the Senior Notes, with a coupon of 5.60%, mature on June 15, 2012. The Senior Notes, with a coupon of 5.60%, mature on June 15, 2042. All other information disclosed in the Original Report remains unchanged.

* * * * *

This combined Form 8-K/A is being furnished separately by Exelon and Generation (Registrants). Information contained herein relating to any individual Registrant has been furnished by such Registrant on its own behalf. No Registrant makes any representation as to information relating to any other Registrant.

This Current Report includes forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995 that are subject to risks and uncertainties. The factors that could cause actual results to differ materially from these forward-looking statements include those discussed herein as well as those discussed in (1) Exelon’s 2011 Annual Report on Form 10-K in (a) ITEM 1A. Risk Factors, (b) ITEM 7. Management’s Discussion and Analysis of Financial Condition and Results of Operations and (c) ITEM 8. Financial Statements and Supplementary Data: Note 18; (2) Constellation Energy Group’s 2011 Annual Report on Form 10-K in (a) ITEM 1A. Risk Factors, (b) ITEM 7. Management’s Discussion and Analysis of Financial Condition and Results of Operations and (c) ITEM 8. Financial Statements and Supplementary Data: Note 12; (3) the Registrant’s First Quarter 2012 Quarterly Report on Form 10-Q in (a) Part II, Other Information, ITEM 1A. Risk Factors and (b) Part I, Financial Information, ITEM 1. Financial Statements: Note 15; and (4) other factors discussed in filings with the SEC by the Registrants. Readers are cautioned not to place undue reliance on these forward-looking statements, which apply only as of the date of this Current Report. None of the Registrants undertakes any obligation to publicly release any revision to its forward-looking statements to reflect events or circumstances after the date of this Current Report.

SIGNATURES

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

June 19, 2012