Geithner, 52, who was an architect of the 2009 bank bailout during the financial crisis, plans to join Warburg Pincus, LLC as its president and managing director and will be "expected to work on mapping the firm's strategy and management, investor relations and on matters related to the firm's investments," according to The Journal.
The 40-year-old firm has invested more than $45 billion in 675 companies worldwide, according to its website.
The Journal has more:
Mr. Geithner has long considered a career in investing once his days in Washington ended. He has been reluctant to take a job with any banks, which he once regulated, and views private-equity firms and other investment managers as different from the institutions he oversaw as New York Fed chief.
Mr. Geithner had been weighing job options while writing an account of the financial crisis, due out next year.
Since leaving public service, Geithner had been traveling on the speaking circuit and speaking at corporate events.