The 35-year-old Boronia man was walking along a footpath on Dorset Road in Boronia, near Boronia Park, about 11pm when he was struck by a Holden Commodore.

Police believe the car was driving south along Dorset Road when it veered onto the wrong side of the road before hitting the pedestrian and his dog.

The car then ploughed through two fences and crashed into a residential unit, injuring both the driver and the passenger.

The pedestrian suffered head and chest injuries, including a collapsed lung and fractures to his arms and legs, Ambulance Victoria spokesman Paul Bentley said.

Paramedics spent 45 minutes treating him at the scene, and he was taken to The Alfred hospital in a critical condition.

The man's dog died at the scene.

The driver, a 29-year-old Kilsyth woman, suffered minor injuries and was taken to Box Hill Hospital, where she is under police guard.

Police expected to interview her on Friday afternoon.

The car's passenger, a 30-year-old man also from Kilsyth, was taken to Royal Melbourne Hospital with serious head injuries.

Dorset Road was closed between Boronia and Hazelwood roads until shortly before 10am on Friday.

Police are investigating the crash and are appealing for any witnesses to come forward.