The crash happened at 6:45 p.m. in the northbound lanes of SR-99 just south of the 1st Avenue Bridge, said Julie Judson with the Washington State Patrol.
The man was pronounced dead at the scene.
Judson says the man was struck by one car traveling in the right lane, and then struck again by a second car in the HOV lane. Troopers don't know why the man was on the highway.
All northbound lanes of SR-99 were blocked for about two hours.
The victim has not been identified.