Durham Regional Police say the accident happened after the 16-year-old put the SUV in neutral while sitting in the driver's seat.
"He tumbled out of the door and was subsequently run over by the rolling vehicle" at his home in the Riston Road and Conlin Road East area of Oshawa," police said in a statement.
Officers rushed to the scene and helped the teen until paramedics arrived. He was transported to local hospital and later transferred to a Toronto-area trauma centre.
Investigators believe alcohol may have played a factor in the accident.