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) July 31, 2012

ACE LIMITED

(Exact name of registrant as specified in its charter)

Baerengasse 32

CH-8001 Zurich, Switzerland

(Address of principal executive offices)

Registrant’s telephone number, including area code: +41 (0)43 456 76 00

Not applicable

(Former name or former address, if changed since last report)

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 (see General Instruction A.2. below):

At the company’s 2012 annual general meeting, the company’s shareholders approved a dividend in the form of a par value reduction payable in four quarterly installments. The dividend approval provides for an annual par value reduction of 1.80 Swiss francs (CHF), which was equal to US$1.96 per share, or $0.49 per quarter, at the time of the annual general meeting. The actual CHF amount for each installment, however, will be adjusted up or down to equal $0.49 near the time of payment, subject to an aggregate cap for the four installments of CHF 2.70, as further described in the company’s proxy statement dated April 4, 2012.

For the first of such installments, in accordance with the shareholder approval, the par value reduction amount was fixed at CHF 0.48 based on the USD/CHF exchange rate of 0.9958 as published on July 25, 2012. Accordingly, the company adjusted its Articles of Association on July 31, 2012 to effect the par value reduction of CHF 0.48. The company’s amended and restated Articles of Association became effective upon registration in the daily register of the commercial register of the Canton of Zurich, Switzerland on July 31, 2012 and, as a result, the company’s par value is CHF 29.79 as of such date.

Accordingly, as expected, the company’s shareholders of record at the close of business on July 31, 2012, will receive the dividend scheduled for payment on August 21, 2012. A copy of the amended and restated Articles of Association is attached hereto as Exhibit 3 and incorporated herein by reference.

Item 9.01 Financial Statements and Exhibits

(d) Exhibits

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: July 31, 2012