It happened February 19 at the Sunoco on the 13000 block of Bustleton Avenue.
Surveillance shows the suspect walking into the store just before 8 p.m.
He approached the counter and demanded money.
The robber then went behind the counter and grabbed the cash from the register.
He took off on foot and was last seen running towards Byberry Road.
Police believe the gas station was robbed by the same man at gunpoint back in February 13.
The suspect is described as a white male, 20-25 years-old, 5'5" tall and 150 lbs. with blue eyes. He was wearing a black hooded sweatshirt, black mask and grey sweatpants.
Anyone with information on this robbery should call police at 215.686.TIPS (8477) or text a tip to PPD TIP (773847).