The robbery occurred Friday at the Wells Fargo branch located at 340-350 South 2nd Street.
Police say the suspect entered the bank, handed the teller a threatening demand note and verbally threatened the teller with a bomb.
After taking an undisclosed amount of money, the suspect fled on foot in an unknown direction.
The suspect is described as a white male, mid to late 30 years-of-age, 5'7 to 5'8, with a thin build, and a beard with mustache. He was wearing a dark colored hooded jacket and a burgundy hat.
Anyone with information is asked to contact Philadelphia Police at 215-686-TIPS (8477), text a tip to PPD TIP (773847) or through PhillyPolice.com.