The collision happened at 4:30 p.m. on Peninsula Road just north of Gregory Road in Muskoka Lakes Township.
The male driver and one male occupant in the vehicle that was travelling north on Peninsula Road were pronounced dead at the scene. The men have been identified as David Lash, 49, and Anthony Lash, 76, of Toronto.
A 13-year-old female passenger was airlifted to a Toronto hospital with non-life threatening injuries.
Peninsula Road in the area of Gregory Road is closed Sunday as the Ontario Provincial Police traffic investigators examine the scene.