Michael T. Doi is of Japanese Canadian heritage. His parents are Takao and Shizue Doi.
He is married to Julia Shin Doi (née Shin), a Korean Canadian lawyer who was herself appointed to the Ontario Superior Court of Justice in 2023. Together they have two daughters, Claire and Anne, who were nurtured by their grandparents Hwa-Seung and Young-Cha Shin (maternal) and Takao and Shizue Doi (paternal).