John W. Magladery was born in New Liskeard, Ontario on October 11, 1911. He graduated from Upper Canada College in 1929 and the University of Toronto Medical School in 1935. As a Rhodes scholar, he received the degree of D. Phil, in Neurophysiology from Oxford University in 1937. During World War II, he was a major in the Royal Canadian Army Medical Corps. Post-graduate studies were undertaken at the University of Toronto and the National Hospital, Queen Square.