"Eddie and I got engaged over the holidays," Rimes tweeted Monday. "That's the news. It's for real this time and the first time EVER!"
Their relationship has made headlines ever since they met on the set of their Lifetime TV movie Northern Lights. At the time, Rimes was married to Dean Sheremet, and Cibrian was married to Brandi Glanville, with whom he has two children.
Rimes and Sheremet separated in September 2009 following reports of her extramarital relationship with Cibrian. The divorce was finalized in December and she moved in with Cibrian, who divorced Glanville shortly thereafter.
"What happened is not who I am, period," Rimes recently said of how their affair played out. "But I do know how much I love him. So I've always said I don't live my life with regret. I can't."