"I came to tell the world that I'm an openly, proud gay man," Sam said to ESPN's "Outside the Lines" and the New York Times.
Sam is expected to be drafted in the upcoming NFL draft. That means he could become the first openly gay player in the history of the NFL.
Analysts say the team that drafts Sam will face unusual challenges.
"He's bringing baggage into your locker room, so when you think about Michael Sam, all of a sudden, can the players handle the media attention that they're going to get?" said ESPN NFL analyst Herm Edwards.
Once word spread of Sam's revelation, he tweeted " I want to thank everybody for their support and encouragement,especially @espn, @nytimes and @nfl. I am proud to tell my story to the world!"
Sam says his teammates have known since August. Current and former NFL players applauded Sam's courage.
ESPN and ABC News contributed to this report.