Police say the masked suspect walked into the store on the 6900 block of Torresdale Avenue just after 3 a.m. and demanded cash from the register.
As the employee opened the cash register, the suspect leaned over the counter and stole an undetermined amount of cash.
He then fled east on Diston Street towards Vandike Street.
The suspect is described as a bald black male. He was wearing a navy blue sweatshirt, black and white bandana, black mask, dark jeans, tan boots and a baseball cap.
Anyone with information is asked to call police at 215.686.TIPS (8477) or text a tip to PPD TIP (773847).