It happened at the Citizens Bank branch on Lancaster Avenue around 12:50 p.m. on Saturday.
Police say the suspect walked in and made a threatening demand to a teller.
After getting an undisclosed amount of cash, he fled the area on foot.
Police say no weapon was displayed and no one was hurt.
The suspect is described as a white male in late 50's to early 60's, 5'05" to 5'06" tall, heavy set, wearing blue jeans, a plain white t-shirt, a white bandana over his nose and mouth, dark sunglasses and a black baseball cap.
Anyone with information is asked to call the Easttown Township Police Department at 610-341-9780.
