A spokeswoman for the firm declined to comment.
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Dewan, with Tiger Global since 2003 and the leader of the firm's investments in public stocks, is leaving at the end of June to start his own investment business, according to the letter. He was the sole portfolio manager of the firm's traditional hedge fund business, which bets for and against stocks.
Watts, with Tiger Global since 2005, is leaving to manage his own money, according to the letter. He had a more general investment role at the firm, working with Dewan and others across a range of strategies.
The departures mean that Scott Shleifer will become the head of Tiger Global's public equity business and Lee Fixel will become the sole head of the firm's private equity business, which he had run with Shleifer, according to the letter. Both are longtime employees of the firm.
Coleman added that he would be "closely involved in the portfolio management and investment research of both businesses and will also maintain primary responsibility for the non-investment functions of the firm," according to the letter.
Tiger Global was launched in 2001 with the financial help of Julian Robertson of Tiger Management, where Coleman worked early in his career. It started off as a traditional hedge fund firm, picking publicly traded stocks, but has since expanded into backing growing private companies with so-called venture capital. High-profile private company investments—some of which went on to big initial public offerings—have included Alibaba, Facebook, Linkedin and Warby Parker.
Today the firm manages about $6.5 billion in hedge funds, about $3.5 billion in funds that only bet just on the appreciation of public stocks, or "long only" funds, and about $10 billion in venture capital, according to a person familiar with the structure.