Deputies and medics were dispatched to the scene, Marine Drive near Hermosa Beach Drive, at about 8:30 p.m. after receiving a report of a serious crash, said Shari L. Ireton of the Snohomish County Sheriff's Office.
Responders found a 47-year-old woman dead at the scene.
A 49-year-old man, believed to be the driver of the vehicle, was seriously injured. He was taken to Providence Hospital for treatment.
Speed and alcohol were both believed to be causing factors, but the incident remains under investigation, Ireton said.
Marine Drive was closed between Hermosa Beach Drive and 83rd Place NW for several hours for the accident investigation, but has since reopened.
The names of the crash victims were not immediately released.