The father brought a motion to change the primary care of his five-year-old son from the mother in Orillia to himself in London.
The child had previously been in week-about care until starting school.
A privately retained assessor recommended the father assume primary care due to the mother's struggles with effective discipline and controlling her household.
The court weighed the benefits of the father's consistent parenting against the risk of separating the child from his mother and siblings.
The court granted the motion, finding that the child's need for consistent discipline to self-regulate his behaviour was paramount, and ordered primary care to the father with a detailed access schedule for the mother.