Sitting down with Andy Cohen on "Watch What Happens Live," the *NSYNC member said he told Spears he was gay back in 2004, on the night of her Vegas wedding, in an attempt to get her to stop crying.
Bass, who later came out to PEOPLE in their 2006 cover story, says after she married Jason Alexander, Spears broke down because she made a mistake.
That's when Bass, who was also in Vegas at the time, went to comfort the singer. Saying Spears was one of the first people he confided in, he describes what went down.
"It was the night that she got married the first time in Vegas to Jason. So I went up to Vegas to kind of see the craziness that was happening," he told Cohen. "And she was a little upset once she realized what she had done because, you know, it was a funny thing.”
“And then she started, like, really crying and, like, she was so upset," he continued.
"And so I took her to her room and we were sitting on her bed and she wouldn’t stop crying, so I was like, ‘I’m gay,'” Bass revealed. “And it made her stop crying… She chuckled.”
Britney Spears got the marriage annulled 55 hours later and kept Bass' secret for years.
Spears and Bass, of course, were tight back in the late 90s/early 2000s when she went on tour with the band during the second leg of "NSYNC in Concert."
She also famously dated one of his best friends, Justin Timberlake, from 1999-2002.
Lance Bass went on to marry Michael Turchin in 2014 after nearly three years of dating.
The ceremony was televised and his bandmates -- Joey Fatone, Chris Kirkpatrick and JC Chasez -- were all in attendance.
Justin Timberlake was headlining the 20/20 tour and wasn't there.