James has been credited with turning the firm into a leading private equity giant.
He oversaw the firm's market listing in 2007 and was an integral part of the GSO takeover that's now the global credit division of the firm.
"We would not have gotten as far as we have, nor would Blackstone be the firm that it is today, without his talent, commitment and managerial strength," the Wall Street Journal reported Co-Founder and Chief Executive Stephen Schwarzman said in a memo sent to employees.
"During his tenure, he helped fundamentally transform and institutionalize the firm," Schwarzman added in the memo, as reported by Reuters.
James joined Blackstone in 2002 as president and chief operating officer.
In 2018, Blackstone's Global Head of Real Estate Jonathan Gray succeeded James to become the new president and chief operating officer at the New York asset management firm.
Gray is reportedly next in line to takeover the reins of Blackstone from Schwarzman, the Journal reports.
Before joining Blackstone, James worked at an investment banking firm Donaldson, Lufkin & Jenrette for 25 years. The firm was later acquired by Credit Suisse First Boston in 2000.
James now plans to devote time to charitable activities, including an organization he established to support students from historically Black colleges and universities, the Journal reports.
James is co-chairman of the Metropolitan Museum of Art and chairman of the finance committee at Mount Sinai Hospital System. He is also board chairman of retailer Costco Wholesale Corporation (COST) - Get Free Report.