Police said the girl was walking near 76th Avenue and 160th Street in the Kew Gardens section of Queens on Monday when a man came up to her, grabbed her buttocks, and then ran away.
Police have a sketch and surveillance video of the suspect.
He has been described as an Indian man in his early 20s, about 5'9", 135 pounds with spiky hair.
This sexual assault follows another attack that happened on Easter Sunday in the Sunnyside section of Queens.
Police are asking anyone with information to call Crime Stoppers at 1-800-577-TIPS.