Police are investigating the cause of a serious crash in Boat Harbour this morning.

Around 9.20am, police responded to a report of a crash between a truck and a car on the Bass Highway.

A white Mitsubishi sedan was stationary on the Bass Highway intending to turn right into Blackabys Road.

At this time, a Kenworth prime mover and trailer travelling east on the Bass Highway impacted with the rear of the sedan.

As a result of the impact, both the car and truck left the road and came to a stop in a paddock adjacent to the highway.

The 60-year-old Sisters Beach man who was driving the sedan was transported by Ambulance Tasmania to the North West Regional Hospital in a critical condition.

The 47-year-old driver of the truck was conveyed to the North West Regional Hospital as a precaution.

The crash is being investigated by Western Crash Investigation Services.

Police are asking for anyone who saw either vehicle prior to or at the time of the crash to contact Senior Constable Adam Lloyd on 6477 7276.