Édouard Gagnon was born in Port-Daniel, Quebec, one of 13 children. He attended a private school and studied art at the University of Montreal. He studied at the major seminary of Montreal, where he received a doctorate degree in theology in 1941. He was ordained in the Society of St Sulpice on 15 August 1940. He then studied at the University of Laval in Quebec from 1941 to 1944, receiving a doctorate in canon law. He attended the Synod of Bishops in 1985 and in 1987, and was given the task of seeking a rapprochement with Archbishop Marcel Lefebvre's traditionalist Society of St Pius X.