The suspect was caught on surveillance walking into the store on the 1800 block of Arch Street at 1 a.m.
He was carrying a white bag with a wooden handle sticking out, possibly a shotgun.
The robber walked up to the counter and lifted the bag to show the gun handle.
VIDEO: Click here for surveillance video
He demanded cash from the register, but the employee refused.
The suspect walked out empty handed and was last seen heading south on 19th Street towards Race Street.
Police later recovered the suspect's jacket.
No injuries were reported.
Authorities believe the same suspect robbed a Center Cuty Dunkin' Donuts back on January 9th.
Police describe the suspect as a black male, 50 years-old, 5'9"-5'11" tall with a medium build and light complexion. He has a salt and pepper beard and was wearing a dark jacket and a blue hooded sweatshirt.
If you see this suspect do not approach him, contact 911 immediately.
Anyone with information on either of these robbers should call police at 215.686.TIPS (8477) or text a tip to PPD TIP (773847).