NBA Commissioner David Stern said in a statement: "Jason has been a widely respected player and teammate throughout his career and we are proud he has assumed the leadership mantle on this very important issue."
While Collins is the first male athlete in a major North American professional league to come out while intending to keep playing, several have previously spoken after they retired about being gay, including the NBA's John Amaechi, the NFL's Esera Tuaolo and Major League Baseball's Billy Bean.
"I think he is immensely brave. I think it's a shame in this day and age he has to be immensely brave, but he is," Amaechi told the AP. "He's going to be a remarkable and eloquent spokesperson for what it is to be a decent, authentic human being — never mind just for gay people."
Rick Welts, president and chief operating officer of the NBA's Golden State Warriors, is openly gay.
"He probably knows what he signed up for. There'll be a whole bunch more television reporters and cameras than he's probably had in the past. ... There had been a long bit of speculation about when, who, how. I think that speculation has been put to rest now," Welts said, "and we'll always remember that Jason Collins was the first man to do this."
Collins says that if he remains in the NBA, he could face uncomfortable reactions from spectators.
"I don't mind if they heckle me. I've been booed before. There have been times when I've wanted to boo myself. But a lot of ill feelings can be cured by winning," he writes.
In February, former U.S. soccer national team player Robbie Rogers said he was gay — and retired at the same time. Rogers is just 25, and others have urged him to resume his career.