Carolyn Kaster / AP file Then Treasury Secretary Timothy Geithner during a news conference at the Treasury Department in 2012.

Former Treasury Secretary Timothy Geithner has landed in the private sector, taking a job as president of the private equity firm Warburg Pincus, the firm announced on Saturday.

Geithner, who was president of the New York Fed at the outset of the financial crisis and has spent much of his career in the public sector, will take an active role in managing the firm.

"In his role, Mr. Geithner will work closely with Warburg Pincus' co-chief executive officers, Charle R. Kaye and Jospeh P. Landy, on overall firm strategy and management, investing and portfolio management, organizational and funding structure, and investor relations," the firm said in a statement.

Warburg's principals first approached Geithner with the idea this summer, the Wall Street Journal reported.

"When they approached me, they clearly wanted me to play a substantive role in helping them manage the firm," Geithner told the Journal.

Geithner worked closely with Treasury Secretary Henry Paulson and the chairman of the Federal Reserve, Ben Bernanke, to devise a response to the crisis while serving as head of the Federal Reserve Bank of New York. He was involved in many of the most pivotal financial decisions of 2008, including the rescue of Bear Stearns, one of the largest global investment banks and brokerage firms, and the collapse of Lehman Brothers. After being appointed Treasury Secretary in 2008,, he also oversaw allocation of $350 billion of funds from the Troubled Asset Relief Program, which was enacted during the administration of George W. Bush.

He stepped down as Treasury secretary last year and was succeeded by Jack Lew. At one point over the summer, Geithner had been seen as a possible replacement for Ben Bernanke as chairman of the Federal Reserve.

Before going to work for the Fed, Geither worked as an assistant financial attache for the U.S. Embassy in Tokyo and had several jobs in the Treasury Department, including under secretary of international affairs, and with the International Monetary Fund.

NBC News' Patrick Rizzo contributed to this report.