Private equity firm The Blackstone Group announced Monday that it plans to buy Strategic Partners, a dedicated secondary private equity unit of Credit Suisse that manages roughly $9 billion in assets.

Simpson Thacher & Bartlett is advising longtime client Blackstone on the deal, while Credit Suisse has turned to a team of attorneys from Schulte Roth & Zabel.

The value of the deal was not disclosed. Strategic Partners has raised more than $11 billion since its formation in 2000 by buying secondary stakes in private equity funds from other investors. Credit Suisse announced last summer that it would look to sell Strategic Partners—as well as another asset-management unit—in an effort to pare back its private equity investments. The Zurich-based bank also announced last year that it would attempt to boost its capital by $15.6 billion.

Blackstone said in a statement that the Strategic Partners acquisition will complement the buyout firm’s existing businesses. The deal is expected to close by the end of this year’s third quarter.

As The Am Law Daily has previously reported, Blackstone is among the biggest Simpson Thacher clients on a roster that includes multiple notable private equity firms. Former Simpson Thacher global M&A head John G. Finley serves as Blackstone’s chief legal officer and is a senior managing director.

The firm advised a Blackstone affiliate in November on the $1.2 billion purchase of hotel investment trust Apple REIT Six. Last year, Simpson Thacher also guided Blackstone to its $1.9 billion acquisition of the discount Motel 6 chain from France’s Accor. Blackstone turned to the firm again for its $9.4 billion deal for Australian mall operator Centro Properties Group in February 2011.

(As we have previously reported, Simpson Thacher was conflicted out of representing Blackstone in connection with the private equity firm’s since-withdrawn bid for Dell Inc. Simpson Thacher is advising Silver Lake Partners, which has teamed with Dell founder Michael Dell on a bid to take the computer maker private, while Blackstone has turned to Kirkland & Ellis.)

For the deal with Credit Suisse, Blackstone has enlisted a Simpson Thacher team led by New York–based corporate partner Brian Stadler.

The Schulte Roth team advising Credit Suisse is led by M&A partner Christopher Harrison and tax partner Philippe Benedict, along with investment management partners Steven Fredman and Joseph Smith. Employee benefits partner Laurence Moss, intellectual property special counsel Scott Kareff, and investment management special counsel Russel Perkins are also advising. The Schulte Roth associates working on the deal are Lauren DeMasi, Lawrence Natke, and Michael Vogel.

Schulte Roth advised Credit Suisse’s asset management division in 2010 on its acquisition of a minority stake in York Capital Management for $425 million.

Last month, Sullivan & Cromwell represented Credit Suisse in connection with its purchase of a Morgan Stanley wealth management division that manages $13 billion in assets and operates in Africa, Europe, and the Middle East. Financial terms of that deal also were not disclosed.