The singer, who has been dating actress Jessica Biel since last February, spent the evening with an unknown woman in New York at the Tribeca Grand Hotel.
A source told the New York Post, "Justin was sitting with a bronze-skinned brunette with long brown hair all night at a cocktail table near the dance floor. They were obviously into each other. It was just the two of them and he had no entourage at all."
Timberlake’s rep refused to comment on the mystery woman. "I have no comment on his personal life."
Earlier this month, there were rumours that Biel and Timberlake were moving in together.