It happened at the store on the 1500 block of Chestnut Street at 6:45 p.m.
Surveillance video shows the suspect walking up to the counter to purchase a coffee.
As the clerk begins to pour a cup, the robber pulls out a handgun and demands all the cash be put into a bag.
However, he was scared off after the employee picked up the phone to dial 911.
Police believe this is the same suspect involved in similar robberies at Dunkin' Donuts and 7-Eleven stores in Center City over the last month.
The suspect is described as a black male, 30-40 years-old, 5'7"-5'9" tall with a medium build and light to medium complexion. He was wearing a dark gray skullcap, dark gray quilted vest with a light gray hooded sweatshirt underneath, carrying a white "Marshalls" shopping bag and armed with a handgun wrapped in a black plastic bag.
If you see this suspect do not approach him, contact 911 immediately.
Anyone with information on this robery is asked to call police at 215.686.TIPS (8477) or text a tip to PPD TIP (773847).