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 23, 2013

Willis Group Holdings Public Limited Company

(Exact name of registrant as specified in its charter)

c/o Willis Group Limited, 51 Lime Street, London, EC3M 7DQ, England and Wales

(Address, including Zip Code, of Principal Executive Offices)

Registrant’s telephone number, including area code: (011) 44-20-3124-6000

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:

Item 5.07. Submission of Matters to a Vote of Security Holders.

On July 23, 2013, Willis Group Holdings Public Limited Company, an Irish public limited company (“Company”), held the 2013 Annual General Meeting of Shareholders (the “2013 AGM”) at the Four Seasons Hotel in Dublin, Ireland. Proxies for the 2013 AGM were solicited pursuant to Regulation 14A under the Securities Exchange Act of 1934, as amended, and there was no solicitation in opposition to the Company’s solicitation.

A total of 158,975,918 ordinary shares (approximately 90.79% of 175,086,511 ordinary shares outstanding and entitled to vote as of May 31, 2013, the record date for the 2013 AGM) were present in person or by proxy, constituted a quorum for the transaction of business, and were voted at the 2013 AGM.

At the 2013 AGM, shareholders elected Mr. Dominic Casserley, Ms. Anna C. Catalano, Sir Roy Gardner, Sir Jeremy Hanley, Ms. Robyn S. Kravit, Ms. Wendy E. Lane, Mr. Francisco Luzón, Mr. James F. McCann, Mr. Jaymin Patel, Mr. Douglas B. Roberts, Dr. Michael J. Somers and Mr. Jeffrey W. Ubben to serve as directors until the next annual general meeting of shareholders or until his/her successor is elected and qualified.

The table below sets out the number of votes cast for and against each director, as well as abstentions and broker non-votes:

The shareholders also ratified the reappointment of Deloitte LLP as the Company’s independent auditors until the close of the next annual general meeting of shareholders, and authorized the Board of Directors, acting through the Audit Committee, to fix the independent auditor’s remuneration. Of the shares voted, 157,978,476 voted in favor, 531,385 voted against and 466,057 abstained.

The shareholders approved, on an advisory (non-binding) basis, the executive compensation of the Company’s named executive officers as disclosed in the Company’s proxy statement for the 2013 AGM in accordance with the Security and Exchange Commission’s rules, including the “Compensation Discussion and Analysis,” the “Summary Compensation” table and related tables and disclosure. Of the shares voted, 134,061,593 voted in favor, 15,622,471 voted against, 1,581,149 abstained and there were 7,710,705 broker non-votes.

Item 9.01 Financial Statements and Exhibits.

(d) Exhibits

SIGNATURES

Pursuant to the requirement 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.

INDEX TO EXHIBITS