Police say it appears the teen poured gasoline on the fire which caused the fire to flash.
A gas can and several chairs were at the scene in the backyard of the home in the Harvey Run neighborhood.
The victim was transported to Christiana Hospital with second and third degree burns to the torso.
Firefighters were dispatched to extinguish the blaze at 5:15 p.m. and called for the helicopter to transport minutes later.
New Castle County Police and the state Fire Marshal will investigate.