It was around 12:48 a.m. when the suspect entered the store located on the 7700 block of Ogontz Avenue.
Police say he pointed a gun at the 63-year-old clerk and said, "Give me everything!"
The suspect made off with $200 and the clerk's wallet. He was last seen fleeing on 78th Avenue.
The gunman is described as a 20-year-old black male, clean shaven, standing around 5'7", and last seen wearing a black hooded jacket.
No one was hurt during the robbery.