Zac Efron and Lily Collins
John Shearer/Getty; C Flanigan/FilmMagic
02/07/2012 AT 07:45 PM EST
Does Zac Efron
have a new special lady in his life?
The actor and Lily Collins
, 22, star of the upcoming film Mirror Mirror
, were spotted enjoying dinner in Los Angeles at STK on Saturday, and they arrived together, according to a source.
"They even walked in holding hands," a source tells PEOPLE of the two, who were at the restaurant for a birthday party for one of Efron's friends.
"They had a drink at the bar together and then joined the birthday crew on the patio," the source adds.
Also hanging out with the birthday party posse: 90210's Ryan Rottman
The same night, Efron
, 24, was spotted partying at Hollywood hotspot Lexington Social House
, where he greeted Miley Cyrus
Two people he definitely isn't dating? Demi Moore
and daughter Rumer
"Me and Rumer have been friends for a long time. I know Demi is going through some personal stuff right now," the actor tells Extra
. "I just wish her well. I hope she's doing okay."
Reporting by JENNIFER GARCIA