It happened at Lee's Discount Beauty on the 5800 block of Old York Road.
Police say the male suspect walked in just before 7 p.m. wearing a mask over his face.
He asked the employees questions about a few products before making a purchase.
As the clerk was placing his item in the bag, the suspect then pulled out a handgun from his pocket and demanded money.
The gunman got away with an unknown amount of cash inside a plastic bag before fleeing the store.
No injuries were reported.
Police describe the suspect as a black male, 5'9" tall with a medium/stocky build. He was wearing a black leather style jacket with a gray hooded sweatshirt underneath, light gray sweatpants, black boots, black ski mask and black gloves.
Anyone with information should call police at 215.686.TIPS (8477) or text a tip to PPD TIP (773847).