Mitchinson trained at York University and quickly became a major figure in the field of Canadian women's history. With Ramsay Cook, she co-edited her first book "The Proper Sphere: Woman’s Place in Canadian Society", a collection of writing on the then new field of Canadian women's history. In 1988, she co-authored "Canadian Women: A History" the first textbook on Canadian women.
Later, she begin to focus on the history of medicine, particularly women's health, and wrote "The Nature of Their Bodies: Women and Their Doctors in Victorian Canada." Her most recent book, "Giving Birth in Canada: 1900-1950", examines the history of childbirth in a Canadian context. As Canada Research Chair, she is conducting research into the history of obesity in Canada.
- "H. B. Atlee on Obstetrics and Gynaecology: A Representative and Singular Voice in 20th Century Canadian Medicine," Acadiensis 32, 2 (Spring 2003): 1-28.
- "Giving Birth in Canada, 1900-1950." (Toronto: University of Toronto Press, 2002).
- "The Impact of Feminism on the Research and Writing of Medical History: A Personal View," Atlantis 25..2 (Spring/Summer 2001): 93-100.
- "The Sometimes Uncertain World of Canadian Obstetrics, 1900 to 1950," The Canadian Bulletin of Medical History, 17, 1-2 (2000): 103-208.
- "On the Case: Explorations in Social History", with Franca Iacovetta (Toronto: University of Toronto Press ss1998).
- "The nature of their bodies: women and their doctors in Victorian Canada" (Toronto: University of Toronto Press, 1991)
- "Essays in the history of Canadian medicine", with Janice P. Dickin (Toronto: McClelland and Stewart, 1988)
- "Canadian Women: a History" with Alison Prentice, Paula Bourne, Gail Cuthbert Brandt, Beth Light, and Naomi Black. (Harcourt Brace Jovanovich, 1988)
- Biography at the Tri-University History Program