The incident happened around midnight, near Vaudreuil, just west of Montreal.
Two men were riding in single file at the river's edge when one of the them went through the ice.
It's not known if the ice cracked under the weight of the snowmobile or if driver strayed onto the river by mistake.
A nearby resident told Radio-Canada that the Ottawa River near Vaudreuil has a strong current and thin ice, making it a dangerous spot for snowmobilers.
Firefighters spent the early morning hours looking for the driver but were unsuccessful because it was still dark outside.
The second snowmobiler was treated for shock.