"I'm a 34-year-old N.B.A. center. I'm black and I'm gay," Collins writes in the May 6 edition of Sports Illustrated, which published the article online Monday morning.
The announcement makes Collins a pioneer of sorts: the first player in the N.B.A., N.F.L., N.H.L. or Major League Baseball to come out while still pursuing his career. Other gay athletes, including the former N.B.A. center John Amaechi, have waited until retirement to divulge their sexuality publicly.
Collins, who split this season between the Boston Celtics and the Washington Wizards, will become a free agent on July 1. He intends to pursue another contract in the summer, which may serve as a test for how N.B.A. teams respond to the announcement.
In his essay, Collins alludes to the situation, writing: "I've reached that enviable state in life in which I can do pretty much what I want. And what I want is to continue to play basketball. I still love the game, and I still have something to offer. My coaches and teammates recognize that. At the same time, I want to be genuine and authentic and truthful."
Collins's decision drew praise and admiration across the athletic and political realm on Twitter.
"I am so proud of my bro @jasoncollins34 for being real," Baron Davis, a former N.B.A. star point guard, wrote on his account.
"Proud of @jasoncollins34," wrote the Lakers star Kobe Bryant. "Don't suffocate who u r because of the ignorance of others."
Chelsea Clinton, who attended Stanford with Collins, also tweeted her support, as did Amaechi, who wrote, "Congratulations to Jason – society couldn't hope for a more eloquent and positive role model."
N.B.A. Commissioner David Stern released a statement welcoming the announcement.
"Jason has been a widely respected player and teammate throughout his career," Stern said, "and we are proud he has assumed the leadership mantle on this very important issue."
All of the major sports leagues have been preparing, to various degrees, for the moment when an active player comes out. The N.F.L., amid speculation that a handful of players were preparing to make the move en masse, has been working with gay advocacy groups to smooth the way for acceptance. The N.H.L. also recently announced a comprehensive program for training and counseling on gay issues for its teams and players.
The N.B.A. has long included education in this area in both its rookie and veteran development programs. League officials have typically played down the need to prepare for an active player coming out, believing that the moment would be greeted with a collective shrug, or should be.
As Stern said in a recent New York Times article, "It's our fervent hope that this draws less attention, not more, when a player eventually comes out."
