The shareholder approval comes after clearance by U.S. antitrust authorities and the European Commission.
Stamford, Connecticut-based Towers Perrin and Arlington, Virginia-based Watson Wyatt expect the merger to take effect January 1. The combined firm will operate under the name Towers Watson & Co.
The merger will create the world’s largest employee benefits consulting firm, with annual revenue of about $3 billion. Watson Wyatt has about 7,500 employees and operates in 33 countries, while Towers Perrin has more than 6,300 employees and operates in 26 countries.
The two firms are especially well known for their expertise in retirement plan and health care consulting. In addition, Towers Perrin offers risk management and reinsurance brokerage services.
“We look forward to completing this transaction, which will create a leading global professional services firm with an enhanced portfolio of services across a range of financial, risk and people management areas,” Watson Wyatt CEO John Haley said in a statement. Haley will be CEO of the combined company.