The incident happened on Sunday at The Crab Shack on 4800 block of North 16th Street.
Police say the employee closing the business gates just before 7 p.m. when he was approached by two men who forced him back inside at gunpoint.
Click here to watch the surveillance video
One of those men went for the safe in the rear of the restaurant while the other watched the two other employees.
The robbers took the entire safe and ran off in an unknown direction.
There's no word on how much money was inside.
The first suspect is described as a black male, 5'8 tall with a thin build and dark complexion. He was wearing a dark colored zip-up hooded sweatshirt with white writing "Old Navy" on the front, black and red Halloween mask over his face, and armed with a handgun.
The second suspect is described by police as a black male, 5'5" tall with a stocky build and light complexion. He was wearing a red and white scarf covering his face, dark colored jacket with white stripes on both sleeves.
Anyone with information is asked to call police at 215.686.TIPS (8477) or text a tip to PPD TIP (773847).