The incident happened at the New Family Grocery Store on the 400 block of West Chelten Avenue.
The suspect was caught on surveillance walking into the store at 12:15 p.m. armed with a handgun and demanding cash.
When the clerk told him the money was in the trunk of her car, he demanded she hand over her keys.
The robber then fled the scene in the victim's vehicle, which police describe as a gold 2008 Nissan Altima with Florida tag number PA2-02Z.
Nothing was stolen from inside the store.
Police describe the suspect as a black male, 40-50 years-old and heavyset with a goatee. He was wearing a dark colored hooded sweatshirt and black pants possible with paint splattered on them.
If you see this suspect do not approach him, contact 911 immediately.
To submit a tip via telephone, dial 215.686.TIPS (8477) or text a tip to PPD TIP (773847).