The incident took place Tuesday afternoon at the Sovereign Bank branch located at 6740 Germantown Avenue in the Germantown section of the city.
The same suspect is believed to be responsible for the armed robbery of the same bank on August 9, 2010.
During Tuesday's robbery, the suspect was dressed in female Muslim garb including a long black dress, a white jacket, and a hijab covering his head and face. He left without taking any money.
During the previous robbery, the subject was wearing a wig and a long dress.
In both incidents, the subject brandished a handgun, threatened employees, and demanded cash.
The suspect is described as a black male in his 30's, 5'6" to 5'8" tall, with a thin build. In the earlier robbery the subject was clean shaven.
He is considered armed and dangerous, and anyone with information is asked to call the Philadelphia Police Department or the FBI's Violent Crime Task Force at 215-418-4000. There may be a reward for information leading to this subject's capture, and tipsters can remain anonymous.