"I'm not engaged period," the singer tweeted on Friday. "Eddie and I felt we couldn't let this rumor go on any longer."
On Thursday, the day after their first television interview as a couple aired on ABC, E! Online reported that the 28-year-old Grammy winner had become engaged to Cibrian.
Their relationship has been tabloid fodder 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.
"Thanks to all of our wonderful fans for the premature congrats," Rimes tweeted, "But for now, let's all be happy we're happy and still and will remain together!"