Police say the suspect entered the Sovereign Bank at 101 East Olney Avenue on at 5:18 p.m. Friday.
He presented the teller with a threatening demand note and fled the bank with an undisclosed amount of cash in an unknown direction.
The suspect is described as a black male, mid 20's, approximately 5'9, thin build, goatee, tattoo under right eye. He was wearing a black hat with fur lining, black wig, silver aviator glasses, multi-colored flannel jacket and blue jeans.
Police consider him armed and dangerous.
To submit a tip via telephone, dial 215.686.TIPS (8477).