Cathy Kinsman says the boy was taken off a respirator Saturday, three days after he was pulled from the snow outside his suburban home.
The Winnipeg Regional Health Authority won't confirm the death, saying it is not information that is made public.
Kinsman says the boy was playing last week when he somehow became buried.
Neighbours rushed to help, dug the unconscious boy out with their hands and performed CPR until paramedics arrived.
Dave MacDonald, a former search-and-rescue technician who runs a survival school, says kids can become trapped by a collapsing snowbank or snow tunnel.
He suggests parents make efforts to monitor their children while they play in the snow, and teach kids to build at least two entrances to any snow tunnel.