Police got a call around 6 p.m. on Friday that two-year-old Dawson Lacroix had disappeared from his family's home in Waterloo, Que., about an hour southeast of Montreal.
He was with a family member outside when he wandered off.
A canine unit and helicopter were deployed to assist in the search, and dozens of volunteers helped. The boy was found unconscious in a water-filled ditch about five hours later.
Sgt. Audrey-Anne Bilodeau of Quebec provincial police said the boy was confirmed dead in hospital.
An investigation into the boy's death is ongoing.