The incident happened on February 20 at 3:45 p.m.
Police say the 13-year-old boy was walking north on the 700 block of North 22nd Street when he was approached from behind by the group.
One of the teens grabbed the boy around his neck and wrestled him to the ground.
They stole his iPhone before fleeing north on 22nd Street.
The victim suffered minor injuries to his lip and left hand.
Police describe the suspects as four unknown black males, 14 to 16 years-old. They were wearing hooded sweatshirts and hooded jackets. Three of the teenagers were carrying backpacks.
Anyone with information on these 4 suspects is asked to call Philadelphia Police at 215.686.TIPS (8477) or text a tip to PPD TIP (773847).
Tips will remain confidential.