The teenager was knocked down on the Mountcharles by-pass.
Gardaí from Donegal Town and ambulance crews attended the scene.
The boy’s condition is now said to be stable.
Earlier four people were hurt in a road accident on the Derry Road in Letterkenny.
Two cars were involved in that incident.
Meanwhile Gardaí in the county are appealing for motorists driving overnight to be extra careful as heavy rain and winds of up to 70km/hr are lashing the county.