John M. Oesterreicher was born 2 February 1904 in Stadt-Liebau, Moravia, then a part of the Austro-Hungarian Empire, into a Jewish family. He studied at the Gymnasium Olmutz, attended the Medical School of the University of Vienna for two years, and studied theology at the Universities of Graz and Vienna. He converted to Roman Catholicism, and was ordained to the priesthood in 1927.

For the next eleven years, his duties were pastoral and editorial. He published a magazine called "Die Erfullung" (The Fulfillment) in which he took a strong stand against Hitler's hatred of Jews; in 1938 he was subjected to interrogation by the Nazis and considered an enemy of the Reich for these views.

After escaping the Gestapo in Austria before the occupation, he continued to combat Hitler's anti-Jewish and anti-Christian ideology through sermons in Paris over the French Broadcasting System. For several decades it was thought these sermons were lost, but transcriptions were discovered and published in 1986 as "Wider die Tyrannei des Rassenwahns" (Against the Tyranny of Race). His first book was also published, "Racisme, Antisemitisme, Antichristianisme", which was confiscated and destroyed by the Nazis. On November 12, 1940 he escaped to the United States, where he republished that book and wrote "Walls are Crumbling" discussing seven major Jewish thinkers.

In 1953 he founded the Institute for Judaeo-Christian Studies at Seton Hall University in South Orange, NJ. Father Oesterreicher and members of the Institute were, in large part, responsible for having the relationship of the Church to the Jewish People made part of the Vatican II agenda. He served as consultor to the Secretariat for Christian Unity during several sessions of the Council and was named an Honorary Prelate in recognition of his work. In 1975 he established the Graduate Department of Judaeo-Christian Studies at Seton Hall University with the belief and hope that deepening knowledge through understanding of Rabbinic tradition, as well as an appreciation for Judaism as a living religion, will guide Christians to join with Jews in mutual respect and solidarity. He saw his two-fold escape from the Gestapo and certain death at the hands of the Nazis as a divine summons to devote his life to nurturing a creative relationship between Christians and Jews.

Msgr. Oesterreicher lectured at various universities in the United States, published several books, and was awarded numerous honors. He died 18 April 1993.