About 11:15 a.m., a man walked into the branch located at 8422 W. Lawrence Ave. and approached a teller's window and demanded cash, the FBI said. The teller handed over the money and the man fled on foot.
Witnesses describe the robber as a white man in his 20s with a goatee. He was wearing glasses, a White Sox hat, a white hooded jacket with gray sleeves and blue jeans, the FBI said.
It was not clear if the man brandished a weapon during the robbery.
Anyone with information about the robbery should contact the FBI Chicago office at (312) 421-6700.