Margaret McCain says the money will go toward the launch of the Margaret and Wallace McCain Centre for Child, Youth and Family Mental Health.
She says the funding will help address gaps in treatment for children and youth, an area she says is "underserved and undervalued."
CAMH says one of the first steps will be to recruit a world-renowned expert to lead the new centre and its programs.
McCain, a child advocate and the former lieutenant-governor of New Brunswick, says she and her late husband have long believed in early intervention when it comes to treating mental illness.
Wallace McCain died of pancreatic cancer last spring. He was co-founder and vice-chairman of McCain Foods and chairman of Maple Leaf Foods.