The Kansas Highway Patrol says a Ford pickup was eastbound on Route 40 when it struck a cow in the road. The truck then went into a ditch, hit an embankment and overturned.
Nicholas Cox was ejected from the vehicle and was pronounced dead at a hospital in Greely County.
The driver, 42-year-old Jeffrey Cox, was taken to a local hospital for treatment.
Authorities say the boy and his father were not wearing seatbelts.