Reuters earlier on Monday had reported that an announcement about the deal was imminent.

New York-based First Eagle manages approximately $100 billion in investment assets. The firm has seven mutual funds with $74 billion in assets under management, according to Chicago-based Morningstar.

While only thirty-three percent of its funds have returned among the top quartile of their peers for the past five years, the firm’s top-performing mutual fund, the $893 million First Eagle Gold Fund, has beaten 95 percent of its category for the past one, three and five years, according to Morningstar.

"We will support First Eagle's management and employees as they seek to provide outstanding investment performance and service to their clients," Joseph Baratta, Blackstone's global head of private equity said in the deal announcement Monday.

Blackstone and Corsair had been in negotiations to acquire the company for several months, as first reported by Reuters in April.

Under the terms of the deal, private equity firm TA Associates is selling its entire stake in First Eagle and the family of John Arnhold, First Eagle's chairman and chief investment officer, will remain shareholders of the firm. TA Associates owns a minority stake in New York-based First Eagle.

The deal announcement marks the end of a long sales process for the firm. TA hired Bank of America Corp in 2013 to explore selling its stake, which is around 25 percent, Reuters reported at the time.

(Reporting by Greg Roumeliotis and Jessica Toonkel in New York; Editing by Bernadette Baum and Meredith Mazzilli)

By Greg Roumeliotis and Jessica Toonkel