Blackstone's COO Tony James sold 4.5 million units at $15 per unit, according to a filing with the U.S. Securities and Exchange Commission.
The units, which represent 8.5 percent of his family's holdings, were sold to fund a portion of Mr.James' substantial obligations to invest in various Blackstone funds, Blackstone said in a statement.
Last week, Blackstone posted a forecast-beating quarterly profit and said it is gearing up for more deals and IPOs as the lending and equity markets recover. The firm said it had $27 billion of capital available for investments.
Blackstone's shares closed at $15.22, down 1 cent, on the New York Stock Exchange.
(Reporting by Jessica Hall; editing by Andre Grenon)