The incident happened on August 19 at the store located at 1 Franklin Town Boulevard.
The robber was caught on surveillance walking up to the counter shortly before 4 a.m. and asking to purchase a carton of cigarettes.
When the 61-year-old male cashier began to scan the cigarettes, the suspect sprayed him in the face with mace or pepper spray and grabbed the cigarettes.
Click here to watch the surveillance video
He then fled the store in an unknown direction.
The clerk was transported to Hahnemann Hospital where he was treated and released.
Police describe the suspect as a black male, 20-years-old, about 6'0" tall with a dark complexion and Afro style hair. He was wearing a camouflage shirt, dark colored shorts and dark colored sneakers.
Anyone with information is asked to call police at 215.686.TIPS (8477) or text a tip to PPD TIP (773847).
You can also submit an anonymous tip online at PhillyPolice.com.