The skateboarder was hit around 2:20 a.m. by a silver Toyota Camry when he tried to cross Airport Way South near South Alaska Street.
The Toyota's driver side headlight and bumper were damaged in the collision and the driver's side view mirror was broken off, said Drew Fowler of the Seattle police.
The car, believed to be a 2011 Toyota Camry LE or SE, never stopped and was last seen heading south on Airport Way South. The skateboarder is in serious condition at Harborview Medical Center.
Anyone with information on the whereabouts of the hit-and-run suspect or the car is asked to call Detective Tom Bacon at 206-684-8932.