Then later on Sunday night, the singer/actor and his Friends With Benefits costar were "pretty inseparable" at another bash thrown by the Weinstein Company and Dewars, an observer says.
But a source insists "they're friends" – period.
As for Timberlake's girlfriend, Jessica Biel, the actress rarely walks a red carpet with Timberlake. But despite their lack of PDA, "Justin and Jessica are definitely together," says the source. "They're happy in their relationship."