The 2 Broke Girls star stepped out with her musician beau Saturday as the two made their first public appearance at the Carousel of Hope Ball in Beverly Hills.
"I'm very lucky my girlfriend has joined me tonight," Groban told Entertainment Tonight. "It's her first time hearing me sing. So I'm going to do some extra warmups tonight so I don't suck."
The pair appeared quite comfortable with each other, with Groban, 33, spotted putting his hand on the small of her back as they explored the event together.
During Groban's set, Dennings, 28, watched "with clear admiration, leaping to her feet to clap and cheer loudly" for him as the performance ended, an onlooker tells PEOPLE.
Post-event, the rumored couple each shared a photo from the red carpet on Instagram, joking that they approve of the romance.
"I ship it," Dennings, who previously dated Nick Zano, captioned the image. Added Groban, "I ship it too."
E! was first to report the news.
I ship it.
I ship it too
Reporting by SCOTT HUVER
I just shipped my pants— josh groban (@joshgroban) October 13, 2014