Officers and medics were called to the scene, at the intersection of Dexter Avenue North and Aloha Street, just after 8 p.m., said Renee Witt of the Seattle police.
Arriving at the scene, they found that the motorcyclist had been thrown several feet in the collision. He was rushed to Harborview Medical Center with critical injuries.
A preliminary investigation found that the 33-year-old motorcyclist was heading north on Dexter Avenue at Aloha Street. At the same time, a Mazda MX6 was heading south on Dexter Avenue.
The Mazda and motorcycle collided at the intersection, throwing the motorcyclist several feet through the air before he landed on the pavement.
The now-riderless motorcycle kept going and slammed into a Honda Civic that was heading south. The impact stopped the motorcycle.
Three women in the Mazda were taken to Harborview Medical Center with minor injuries.
All three drivers involved in the crash were evaluated for signs of impairment, and it is not believed that alcohol or drugs played a role in the collision, Witt said.