Major Crash officers are investigating a fatal crash near Balingup on Friday.
Police say a white Toyota Hiace van and a white Hyundai collided on South West Highway near Grimwade Road in Balingup about 4.45pm.
A 25-year-old male passenger of the Hyundai died at the scene of the crash.
The 23-year-old male driver of the Hyundai was taken to Royal Perth Hospital with serious injuries.
The 18-year-old male driver of the Toyota was treated for minor injuries and was taken to Bridgetown Hospital.
Major Crash investigators are seeking witnesses who may have seen either vehicle driving in the Balingup area prior to the crash.
Anyone with information that may help police with their enquiries is urged to call Crime Stoppers on 1800 333 000 or make a report online at www.crimestopperswa.com.au