The robbery occurred at the PNC Bank at 301 West Trenton Avenue on Thursday.
Police say the suspect entered the bank around 3:40 p.m. carrying a smallish silver revolver, approached the teller, and demanded money.
After obtaining an undisclosed amount of money, he fled on foot.
The suspect was last seen heading east on West Trenton Avenue.
Police describe the suspect as a black male, mid-20s, approximately 5'11, medium build, medium to dark complexion, wearing jeans, a black hooded sweatshirt, and possibly a scarf or shirt over his face
No injuries have been reported.
Anyone with information should call the FBI at 215-641-8910 or Falls Township PD at 215-949-9111