The history of the Johann-Adam-Möhler-Institute cannot be thought without the ecumenical pioneers of the church of Paderborn. At the Philosophical-Theological Academy, above all the professors Paul Simon, Adolf Herte and Norbert Peters had already laid the crucial groundwork for an approach between the separated churches before the Second World War.

Simon was one of the first Catholic authors who dealt with the ecumenical movement. On the Catholic part he conducted the first interdenominational conference of theologians. Herte submitted an important study about the development of the Catholic image of Luther. Peters in his function of an Old Testament theologian, promoted the encounter with Protestant exegesis and essentially contributed to the establishment of textual criticism in the Catholic area. Simon, dean of the cathedral since 1933, and Lorenz Jaeger, archbishop since 1941, maintained numerous ecumenical contacts in the time of the Third Reich which had to be kept hidden to a great extent because of the secret police surveillance. In 1943, the two succeeded in the establishment of an ecumenical department of the Bishops’ Conference, the management of which was transferred to Jaeger and to the Viennese Cardinal Innitzer. Even in the last year of the war, theological groundwork for conversations with the Protestant side was started in which, among others, Karl Rahner, Romano Guardini and Michael Schmaus were involved.

As a result of this groundwork, the so-called Jaeger-Stählin-Circle (ecumenical study group of Lutheran and Catholic theologians) was founded in 1946 which furthers the discussion with Lutheran theologians until today. The members of it were respectively are, among others, Wolfhart Pannenberg, Karl Lehmann, Joseph Ratzinger and Eduard Lohse. Paderborn was getting to be a laboratory of dialogue with Protestantism (like Vienna for the dialogue with Orthodoxy). Finally, Jaeger was substantially involved in the initiative to establish the Vatican Secretariat of Unity and in its conception (1960). Supported by Prof. DDr. Eduard Stakemeier, Director of the Möhler-Institute, he can be regarded as one of the fathers of the Decree on Ecumenism of the Second Vatican Council. Due to his commitment to the unity of the Church, he was elevated to Cardinal in 1966.

In order to promote the encounter between the separated Christians, the „Association for the promotion of academic research in the field of studies in denominations and diaspora“ was brought into being on 27 January 1956. The main objective of the association was the establishment of an institute that should encourage the research in the sphere of ecumenical theology. In 1969, it was renamed in „Association for the Fostering of academic research in the field of Ecumenics“.

The Institute for Studies in Denominations and Diaspora was founded on 19 January 1957 by Archbishop Lorenz Jaeger. It has been named after the theologian Johann Adam Möhler (1796-1838) from Tübingen (later on Munich) being the first who introduced the academic research of doctrinal differences between the major Christian denominations to Catholic theology. In 1966, the original title "Institute for Studies in Denominations and Diaspora“ was changed into "Institute for Ecumenics". It is linked to the Faculty of Theology in Paderborn.