Scott Eastwood, the hunk in the new movie "The Longest Ride," revealed on Thursday night's "Watch What Happens Live" that Ashton Kutcher cheated on Demi Moore with his then girlfriend.

The shocking claim came about when a caller asked fellow guest Jon Cryer what it was like working with Ashton Kutcher on "Two and a Half Men" since Cryer once had a relationship with Demi Moore. (Cryer and Moore briefly dated in the 1980s.) Cryer admitted it was a bit "awkward," but "it was cool" because Ashton already knew he and Moore had dated in the past. This is when Eastwood shared his thoughts on what caused the Moore and Kutcher divorce.

"If it makes you feel any better, he did sleep with one of my ex-girlfriends -- but she was my current girlfriend at the time," Eastwood said.

"Watch What Happens Live" host Andy Cohen appeared shocked at the revelation and asked if his ex was "the girl in San Diego." Eastwood confirmed that she was.

"Well, I think it was the catalyst that broke him and Demi up," Eastwood added.

In September 2011, Eastwood was dating Sara Leal, the woman who Kutcher allegedly cheated on Moore with at the Hard Rock Hotel in San Diego during the couple's sixth wedding anniversary, reports Daily Mail. Kutcher has never publicly admitted to having an affair, but Leal has openly expressed regret many times. She has said Kutcher duped her because he told her that he and Moore were separated at the time.

Leal told FOX411.com, "I don't watch television and I read very few magazines. It never crossed my mind that he was married. But then he said he was separated, which still doesn't make things okay, but I wasn't thinking clearly."

In 2013, the Texas-born beauty warned Mila Kunis not to trust the "Two And A Half Men" star.

"Once a cheater, always a cheater," Leal told The Sun. "If I were Mila, I'd be careful. He doesn't have the best track record. But she's obviously willing to take that risk."

Eastwood said he bears Kutcher no ill will, and if the two ever met, he would "shake his hand."

Eastwood stars in the new movie "The Longest Ride," which premieres in U.S. theaters on Friday.