It happened at the TD Bank at 214 Wilmington-West Chester Pike in Concord Township around 4:50 p.m.
After the robbery, police say the suspect fled the bank west on Beaver Valley Road into the Johnson Farm Lane apartment complex.
The suspect is described as a white or Asian man standing 5'2" to 5'6" tall.
He was wearing a black jacket, tan pants, black shoes and a black hat. He was also covering his face with a black cloth.
Police ask anyone with information, including anyone at Johnson Farm Lane apartments who may have seen the man, to call (484) 840-1000.