The wreck happened at about 8:40 p.m. in the 18200 block of Green Valley Road, according to Tim Perciful with King County Fire District 44.
Medics originally ordered two airlifts for the injured drivers and passengers, but Perciful said they were cancelled because they would have taken too long.
Instead, all four were taken by ambulance to Harborview Medical Center. Two of them are in serious condition, and the other two are in critical condition, according to Cindi West with the King County sheriff's office.
A stretch of the road around the crash site will be closed well into Tuesday night as the King County Major Accident Response and Reconstruction Team investigates.
It's so far unclear what caused the crash or if drugs or alcohol played a role.