It happened on August 27 at the store on the 1900 block of East Hunting Park Avenue.
Police say a 17-year-old girl was working at the walk-up window around 9:30 p.m. when an unknown male riding a black bicycle approached and ordered some water ice.
When the employee returned, the suspect was pointing a handgun at her and demanding cash.
Click here to watch the surveillance video
She ran to the back of the store and told a co-worker what happened. Both stayed in the back until the suspect left.
No injuries were reported and nothing was taken during the robbery.
Police describe the suspect as a black male in his early 20s with a thin build and dark complexion. He had a scriffy beard and was wearing a grey hooded sweatshirt. He was also riding a black trick bike with red extended foot pegs, and was armed with a handgun.
Anyone with information should call police at 215.686.TIPS (8477) or text a tip to PPD TIP (773847).