It happened around 5:00 p.m. Monday on the 6200 block of Kingsessing Avenue.
Police say a man in his 30s was standing on the shoulder of the westbound lane. He was working on his bike when he was struck by a vehicle.
According to authorities, the driver briefly stopped then kept going.
The victim was taken to the Hospital of the University of Pennsylvania with severe head injuries.
The striking vehicle is described as a black 2000-2004 Jeep Cherokee, possibly missing a headlight.
Anyone with information regarding the accident should contact Philadelphia Police AID at 215-685-3180 or dial 91.