Jason Collins (left) revealed that he is gay in April. (@JoeKennedy)

Delivering on a promise he made in an essay for Sports Illustrated in which he revealed that he was gay, Wizards free-agent center Jason Collins marched in Boston's annual pride parade on Saturday.

Wearing a black Nike shirt with rainbow lettering that read "#BETRUE", Collins joined his former college roommate and current Massachusetts congressman Joe Kennedy at the event, which drew thousands of attendees and is in its 43rd year. WCBV.com reported that Boston's parade drew 230 groups this year, making it the second-largest such event, trailing only New York City.

“I’m a 34-year-old NBA center,” Collins wrote in an April piece with Franz Lidz. “I’m black. And I’m gay. 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.”

With that declaration, Collins became the first active openly gay male athlete in the four major American sports leagues. He said Boston's pride parade was a major impetus for his decision to reveal his sexuality.

I realized I needed to go public when Joe Kennedy, my old roommate at Stanford and now a Massachusetts congressman, told me he had just marched in Boston's 2012 Gay Pride Parade. I'm seldom jealous of others, but hearing what Joe had done filled me with envy. I was proud of him for participating but angry that as a closeted gay man I couldn't even cheer my straight friend on as a spectator. If I'd been questioned, I would have concocted half truths. What a shame to have to lie at a celebration of pride. I want to do the right thing and not hide anymore. I want to march for tolerance, acceptance and understanding. I want to take a stand and say, "Me, too." The recent Boston Marathon bombing reinforced the notion that I shouldn't wait for the circumstances of my coming out to be perfect. Things can change in an instant, so why not live truthfully? When I told Joe a few weeks ago that I was gay, he was grateful that I trusted him. He asked me to join him in 2013. We'll be marching on June 8.

Jason Collins poses with his former college roommate before Boston's annual pride parade. (@JasonCollins34)

Collins, 34, was a first-round pick in 2001 after spending four years at Stanford. His 12-year NBA career has included stops with the Nets, Grizzlies, Timberwolves, Hawks, Celtics and Wizards. Collins’ twin brother, Jarron, retired in 2011 after a 10-year career with the Jazz, Suns, Clippers and Blazers.