In 1948 he was named vice-rector of the seminary in Königstein (Taunus) for seminarians from what was then East Germany. He was a student of Michael Schmaus, who directed his doctoral dissertation on The Mystery of Mary in the Devotion and Doctrine of the Carolingian Era. He later taught at Tübingen and was professor of dogmatic theology at the Ludwig Maximilian University of Munich from 1965 until his retirement in 1985.

An internationally renowned theologian, he wrote over 80 books, 500 papers, 400 book reviews and countless articles. He edited the Münchener Theologisches Zeitschrift (1966-1984) and was a consultor to the Pontifical Council for the Family and the Commission on Faith of the German Bishops' Conference.

Created and proclaimed Cardinal by John Paul II in the consistory of 21 February 2001, of the Deaconry of St. Francis Xavier at Garbatella.

Cardinal Leo Scheffczyk died on 8 December 2005.