UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, DC 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) July 29, 2015

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:

Section 8 – Other Events

Item 8.01 Other Events.

As previously disclosed, on April 29, 2014, Exelon Corporation, a Pennsylvania corporation (“Exelon”), entered into an Agreement and Plan of Merger (the “Original Merger Agreement”) by and among Exelon, Purple Acquisition Corp., a Delaware corporation and a wholly owned subsidiary of Exelon (“Merger Sub”), and Pepco Holdings, Inc., a Delaware corporation (“PHI”). The Original Merger Agreement was amended and restated by the Amended and Restated Agreement and Plan of Merger, dated as of July 18, 2014, among Exelon, Merger Sub and PHI (the “Merger Agreement”).

On July 29, 2015, Exelon elected to extend the termination date of the Merger Agreement from July 29, 2015 until October 29, 2015 pursuant to Section 8.2(a) of the Merger Agreement. No other provisions of the Merger Agreement were otherwise amended or waived, and the Merger Agreement remains in full force and effect. A copy of the notice that Exelon provided to PHI concerning the extension is attached as Exhibit 2.1 to this Current Report on Form 8-K.

The proposed merger also remains subject to approval by the public service commission of the District of Columbia. Following the expiration of the U.S. Department of Justice’s review period on December 22, 2014, the Hart-Scott-Rodino Act no longer precludes completion of the merger. Exelon and PHI expect to complete the merger in the third quarter of 2015.

Item 9.01. Financial Statements and Exhibits.

(d) Exhibits.

The following items are included as Exhibits to this report:

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Cautionary Statements Regarding Forward-Looking Information

This report contains certain 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 the forward-looking statements made by Exelon include those factors discussed herein, as well as the items discussed in (1) Exelon’s 2014 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 22; (2) Exelon’s Second Quarter 2015 Quarterly Report on Form 10-Q (to be filed July 29, 2015) in (a) Part II, Other Information, ITEM 1A. Risk Factors; (b) Part 1, Financial Information, ITEM 2. Management’s Discussion and Analysis of Financial Condition and Results of Operations and (c) Part I, Financial Information, ITEM 1. Financial Statements: Note 19; and (3) other factors discussed in filings with the SEC by Exelon. Readers are cautioned not to place undue reliance on these forward-looking statements, which apply only as of the date of this report. Exelon does not undertake any obligation to publicly release any revision to its forward-looking statements to reflect events or circumstances after the date of this report.

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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 hereunto duly authorized.

July 29, 2015

EXHIBIT INDEX