Collins, who played with the Boston Celtics and Washington Wizards this season and is now a free agent, made the announcement in an interview with Sports Illustrated, published on Monday,
"I didn't set out to be the first openly gay athlete playing in a major American team sport. But since I am, I'm happy to start the conversation.
"I wish I wasn't the kid in the classroom raising his hand and saying, "I'm different." If I had my way, someone else would have already done this. Nobody has, which is why I'm raising my hand," he added.
The 34-year-old has played for six teams in the NBA and reached the NBA finals twice and says he intends to continue in the sport.
Former US President Bill Clinton, whose daughter Chelsea was a classmate of Collins at Stanford University, issued a statement applauding Collins for coming out.
"Jason's announcement today is an important moment for professional sports and in the history of the LGBT community," Clinton said.
"It is also the straightforward statement of a good man who wants no more than what so many of us seek: to be able to be who we are; to do our work; to build families and to contribute to our communities. For so many members of the LGBT community, these simple goals remain elusive.
"I hope that everyone, particularly Jason's colleagues in the NBA, the media and his many fans extend to him their support and the respect he has earned."