Philadelphia police were called to the scene around 11:15 p.m. Sunday at 63rd and Callowhill streets.
Police say the 24-year-old father was riding a minibike with his son. They say the bike was not registered or street legal. It had no lights and the father and son weren't wearing helmets.
The two were going south on 63rd when a northbound SUV struck the pair as it was turning left onto Callowhill.
Arriving police and medics found multiple people lying in the roadway.
The unresponsive 6-year-old boy was taken to Children's Hospital of Philadelphia where he was pronounced dead a short time later.
Police say the 28-year-old male driver appeared impaired. They say he was driving with a suspended license. He was taken to Penn Presbyterian Medical Center for treatment.
Police say they found a bottle and can of beer in the SUV. The driver is expected to be charged with DUI.
The father was taken to Lankenau Medical Center for injuries to his head, hip and leg. Doctors say he had to have one leg partially amputated.
If he survives, police say the father may face charges for putting his child in danger.