The girl, whose identity was not released, was playing at the 181-25 Hillside Ave. eatery when a man sexually assaulted her about 8:30 p.m., according to the NYPD.
The girl did not appear to have been injured.
The man, who may be in his 20s, was last seen wearing a brown or purple polo shirt, dark jeans, white sneakers, police said.
The suspect, who can be seen on surveillance footage, also had what could be a bandage or some sort of lump on his forehead, cops said.
Anyone with information is asked to call Crime Stoppers at (800) 577-TIPS (8477).