Josh Groban hid his impressive singing skills from his new girlfriend Kat Dennings until this past weekend when the couple made their first public appearance.

"I'm very lucky my girlfriend has joined me tonight," Groban told Entertainment Tonight at the Carousel of Hope Ball in Los Angeles on Oct. 11. "It's her first time hearing me sing. So I'm going to do some extra warmups tonight so I don't suck."

Groban and Dennings do sing together sometimes, but he never uses his real pipes.

"I mean, just kind of like, we joke sing all the time, you know, we just, we harmonize on the radio, but no I haven't really done, it always seems like a cheesy move on my part. I don't really sing for her. Like, 'Hey you want to hear me sing?'" the "You Raise Me Up" singer said. "So it's nice that we can both come out and support and then also as an added bonus I get to sing for her also."

The "2 Broke Girls" star also bragged about her new man in an Instagram photo with Groban on the red carpet. She captioned the pic, "I ship it." Groban returned the favor with another photo of the couple and captioned his, "I ship it too."

Groban previously dated January Jones for two and a half years starting in 2003. He also had a close relationship with Katy Perry, but insists they were just good friends. Dennings was dating actor Nick Zano earlier this year.