During a Sunday appearance on Watch What Happens Live with Andy Cohen, Frankel revealed the breakup happened just a few weeks ago.
"They're in different places in their lives and they were headed down different paths," a source told Us of the split. "They were cohabitating for a bit, but are not anymore."
Frankel, 44, was reportedly first spotted with Cerussi, 35, in public back in January 2014. They were also photographed vacationing together in Miami as recently as two months ago.
Although Frankel came right out and said she never plans to marry legally again, she's still keeping her options open and would be willing to commit to someone off paper.
"She's been dating other people," the source said. "She'd be happy in a committed relationship with someone new, but truly doesn't want to get married again."
Frankel was previously married to Jason Hoppy, whom she had a brutal custody battle with over their four-year-old daughter Bryn and separated in 2012, and Hollywood producer Peter Sussman before him.
"I don't know what I'm looking for, and I don't know if I'm looking for anything," Frankel reportedly told Cohen on Sunday's WWHL episode. "I think the kind of guy that I would need to be with has to be able to handle me, which is a tall order."
Prior to her The Real Housewives return, Frankel starred on her own talk show Bethenny in addition to the Bravo series Bethenny Getting Married and Bethenny Ever After?.