Stifel Financial Corp., the investment bank known for snapping up regional rivals and Wall Street castoffs, agreed to buy Eaton Partners to add ties with hedge funds, private-equity firms and high-net-worth family offices.

Eaton works with more than 4,000 institutional investors, and has raised $25 billion for funds in the past five years, St. Louis-based Stifel said in a statement Monday that didn’t disclose terms. The purchase will help Stifel expand its investment-banking and wealth-management operations, the firm said.

Stifel also agreed this year to buy Barclays Plc’s U.S. wealth-management operation, adding almost 200 financial advisors and boosting the business that accounts for more than half of the firm’s revenue, according to data compiled by Bloomberg. Chief Executive Officer Ronald Kruszewski has made more than two dozen takeovers since he’s taken charge in 1997, including the acquisition of rival brokerage Sterne Agee in June.

“Charlie Eaton and his team are placement experts with a large investor base and a track record of success,” Kruszewski said in the statement. “We look forward to expanding our core advisory business and leveraging direct placements with our high-net-worth platform.”

The deal will help the investment bank advise middle-market clients on raising capital in both public and private markets, Stifel Co-President Victor Nesi said in the statement. The transaction is expected to be completed in January, according to the statement.