Cibrian was by Rimes' side last night when she sang "White Christmas" at the L.A. Live tree-lighting ceremony and opening of the L.A. Kings ice skating rink in downtown Los Angeles.
The two were first spotted on a side of the stage just minutes before Rimes' performance.
Rimes, who was wearing a skin-toned Stella McCartney minidress, talked on stage about spending the holidays with family, but...
She made no mention of her beau. Cibrian could be seen watching Rimes on a large screen across the rink and chatting and laughing with an older gentleman.
But when Rimes sang, Cibrian was completely silent, standing with his arms crossed, chewing gum and keeping a very straight face.
Rimes remained on stage for the tree lighting, but quickly made her way over to Cibrian at the close of the ceremony. They walked away holding hands.
We're told the couple joined a small group for dinner at nearby Katsuya.
As for Cibrian's latest drama, Scheana Marie tells Access Hollywood that she and the actor began an affair three years ago but it ended when he began seeing Rimes.
—Reporting by Brett Malec
Talking about alleged cheats, check out our Tiger Woods and Family photo gallery.