The pair were also seen kissing and cuddling closely while on a date at a lounge, reported Us magazine.
"They were affectionate most of the night," a source said.
According to the source, the actress "was touching his knee" at their VIP table.
"They were a little more obvious outside the venue after they were leaving," the source added.
The stars have yet to comment on the nature of their relationship, though another insider said, "They've been seeing each other quietly in New York, where they both live."
Radcliffe split from his production-assistant girlfriend Rosie Coker in October 2011.
