From the very beginning Canon Law was taught by the Theological Faculty until both programs separated in accordance with the Apostolic Constitution Deus scientiarum Dominus in 1929.

In 1890 the rector Jean Baptiste Abbeloos appointed the German Bernard Jungmann to the newly organized Cours pratique d'histoire ecclésiastique.

In the same year the Hoger Instituut voor Godsdienstwetenschappen (Higher Institute for Religious Studies) was established, where a theologian such as Edward Schillebeeckx briefly taught dogmatics.

Leuven theologians also worked closely together with the Belgian episcopate, led by Cardinal Leo Joseph Suenens, in Rome during the preparations for and the actual sessions of the Second Vatican Council (1962–1965).

Many of these theologians exerted a decisive influence upon a number of council documents (including Sacrosanctum Concilium, Gaudium et spes, Dei verbum, Nostra aetate, and particularly Lumen gentium, among others).

This was made possible through their expertise, their willingness to collaborate with others (e.g. theologians such as Yves Congar were offered lodging at the Pontifical Belgian College in Rome) and by holding several key positions (e.g. Msgr.

Gerard Philips' role as adjunct-secretary of the Doctrinal Commission made him into the key architect of Vatican II's Dogmatic Constitution on the Church).

This came to expression, among other ways, in the so-called Leuven Flemish-movement, and the linguistic conflict led to the splitting of the University into a Dutch-language and a French-language part in 1969; As a result, the Theological Faculty was also split in two: the Dutch-language faculty remained in the Flemish town of Leuven and the French-language group went to be a part of the newly established Université Catholique de Louvain in Louvain-la-Neuve.

Preeminently, the professor corps was divided, and henceforth it became a Dutch-language education and research body, along with an international English-language program.