Washington State Patrol Trooper Krista Hedstrom said the head-on crash happened around 6 p.m. on SR 305 at George Lane between Poulsbo and Bainbridge Island.
She said a woman driving northbound crossed the center line, slamming into another car.
The woman and a man who was driving the victim vehicle were airlifted to Harborview Medical Center with critical injuries. A female passenger in the victim vehicle died in the crash.
Just moments before the crash, a tipster called police after he saw the woman driving erratically and with an extremely flat front tire.
It's unclear what role the flat tire played in the wreck, but Hedstrom said alcohol was likely involved and the female driver is now being investigated for vehicular homicide.
Traffic on SR 305 near the crash was blocked until after 10 p.m.