The robbery took place just after 2:40 p.m. at the bank branch located at 1818 Market Street.
Police say a man entered the bank and passed a demand note to a teller. After obtaining an undisclosed amount of cash, the suspect fled the bank.
He is described by police as a black male in his mid to late 50s, approximately 6', medium build, with a medium complexion and full "salt and pepper" beard.
He wore a black baseball hat with a purple brim and unknown logo, a black coat, and brown-framed eyeglasses.
The suspect is considered armed and dangerous.
Anyone with information about this robbery or the suspect is urged to call the FBI at 215-418-4000 or the Philadelphia Police Department.
Police say there may be a reward for information leading to the suspect's capture.