The deal marks the board's first ownership stake in a private equity manager or any investment management company, said Dennis D. MacKee, communications director.
The board oversees a total of $138.4 billion, including the $112.2 billion Florida Retirement System.
The deal closed June 18, after about two years of work, Mr. MacKee said.
Evercore Partners, the board's consultant on investing in general partnership management companies, assisted. Mr. MacKee said board officials won't comment on whether they are pursuing other ownership stakes, although he said there is no deal pending.
The board has $2.1 billion invested in private equity with Lexington, consisting of $1.5 billion as a co-investor and $600 million in Lexington funds 4, 5, 6 and 7, Mr. MacKee said. The board has been making investment commitments with Lexington since 1998, Mr. MacKee said.
Thomas Gianetti, Lexington CFO, couldn't be reached for comment.