Domenico Rosati, 84, has been found safe near Quebec City.
Drivers called police after they spotted a car moving very slowly on a highway.
When police pulled the driver over they noticed it was the missing 84-year-old Lasalle man.
Rosati had been missing since Friday morning after he dropped off one of his grandchildren in front of Lasalle Community Comprehensive High School.
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Luca Mascetti says his grandfather has memory issues and takes medication for diabetes, which he believes his grandfather may not have taken.
Rosati drives a blue 2005 Pontiac Pursuit with plate number P55AFF.
Family members had joined police in their search efforts, combing through the Montreal borough of Lasalle.
“It was a very long night and a very long day. We’re very relieved,” Mascetti told Global News.