There were seven people in the grey Ford Falcon sedan – including two riding in the boot – when it crashed in Kalgup, two and a half hours south of Perth just before 8.50pm.
Investigators believe the 17-year-old driver lost control of the car on a bend in Doyle Road, sending the vehicle flying off the road.
Two rescue helicopters were rushed to the scene along with police, Fire and Emergency Services and St John Ambulance.
Two passengers, boys aged 15 and 16, died at the scene.
The 17-year-old girl who had been behind the wheel was airlifted around 200km in a RAC helicopter to the Royal Perth Hospital with serious injuries.
The remaining passengers – one girl and three boys aged 15 to 16 – were taken to hospitals in Busselton and Bunbury.
This content first appear on 9news