The pair were in a car swept off a road by a torrent of water on Saturday after heavy rain led rivers and streams to overflow their banks in the region around the town of Massa Marittima.
Yannick’s father, an amateur triathlete from the canton of Bern, was discovered by divers about a kilometre from where the car left the road, the Italian news agency Ansa reported.
Rescuers found the boy on Monday, seven kilometres away, after an extensive search operation involving helicopters, search dogs, divers and fire fighters, according to local media reports.
Mudslides and high water in the region's network of canals and streams complicated the operation.
Officials found the car on Sunday jammed under the arch of a small bridge just 150 metres away from the road.
The Bern man was vacationing with his wife and son, joining a group of around 20 triathletes.
Yannick’s 43-year-old mother got out of the car and walked to their holiday home at a farm just before the wall of water carried the vehicle away.
According to Ansa, her husband was in the process of parking the car when the accident occurred.
She escaped injury but was treated for shock.
The heavy rain and flooding forced numerous evacuations of homes in the southern Tuscany region over the weekend, while more than 100 rescue operations took place.