In the early years, the project group worked in Akademiestraße.

In founding a project group, the MPG had responded to a request by Prof. Dr. Georg Wannagat (1916-2006), President of the Federal Social Court from 1969 to 1984. In the summer of 1972, he had written a letter to the then President of the MPS, Reimar Lüst (1923-2020), suggesting that comparative and international social law be included in the research programme of the Max Planck Society. In doing so, Wannagat pursued the goal of dragging social law out of the "academic offside". Efforts to bring social law closer to the academic sciences had already been made in the late 19th century. During the Nazi and post-war periods, however, these efforts almost completely disappeared into insignificance. Until the project group was founded, social law research in the Federal Republic of Germany (FRG) had hardly been conducted – certainly not with regard to fundamental issues. However, the passing of a large number of new social laws in the then FRG and the resulting court decisions made this necessary, as did an increasingly active role for Germany on the international stage. The FRG's membership in associations such as the United Nations, the World Health Organization, the European Community and the Council of Europe went hand in hand with inter- and supranational obligations, which is why the academic development of international social law (bi- and multilateral treaty law and the law of international organisations) and the freedom of movement-specific social law of the European Communities became increasingly urgent.

Wannagat would have liked to see the Max Planck researchers working in Kassel, the seat of his court. However, Bavarian-born LMU professor Hans F. Zacher (1928-2015), who had been chosen to lead the group, did not want to relocate to Kassel. After lengthy negotiations, the Max Planck Project Group for International and Comparative Social Law finally began its work in Munich on 1 March 1976.

The researchers exchanged ideas at regular meetings.

The Project Group had to start at "ground zero" and dare to enter uncharted scientific territory. There was hardly any research to build on and initially not even a library. To systematically record social law and to work out its peculiarities – not only for Germany, but also comparatively for other countries – was the central task the researchers were confronted with.

As the only research group of its kind in the world, Zacher and his colleagues did pioneering work. The researchers not only had to develop the methodology and system of social law research from scratch. They also had to determine what is meant by social law in the first place. A series of ground-breaking academic publications on the principle of the welfare state, on the origins of social insurance and on the Social Code successively approached the topic. The researchers closed in on their complex subject matter from two sides: through thematic foci on the one hand, and research into the social law of other countries on the other. Initially, the focus was on France, Great Britain, Italy, Canada, the GDR, the Soviet Union and Algeria. Important topics in the first years were, above all, the procedure of social benefits provision, social protection in the case of disability, social protection for authors and artists, as well as the legal status of social workers. Special importance was attached to research on social insurance. This eventually resulted in a large colloquium on the occasion of the 100th anniversary of the "Imperial Message", which had introduced social insurance legislation under Bismarck in 1881.

In 1982, the Institute moved to Leopoldstrasse, where research was carried out until 1999. The Institute then moved to Amalienstrasse. Since fall 2023, it is located at Marstallstr. 11.

Four years after its foundation, the Project Group became a full-fledged institute in 1980, with foreign and international social law as its research subject. This step enabled Hans F. Zacher to recruit further researchers and to expand the thematic focus. Questions of social law concerning medical care, social welfare, old-age security, marriage and family, as well as social security in the public sector now occupied the meanwhile ten academic staff members. The work on individual problem areas was intended to spur the general development of theory and to test its accuracy.

In newly founded country departments, the social law of further countries or regions was explored, including the Scandinavian countries, Spain, the USA, Canada and Kenya – to name but a few. From the beginning, specific emphasis was placed on researching social law in countries that are particularly exemplary for current development and reform processes. In doing so, the comparison of social law has always served national social policy by highlighting the strengths and weaknesses of its own system. In addition, the Institute took up international social law, i.e. the regulation of cases relating to cross-border situations such as the payment of social benefits abroad or the socio-legal position of foreigners, and deepened its research on international organisations. In this context, a fundamental paper on the social aspects of United Nations law was published in 1987.

The supranational law of the European Community was of particular importance. In particular, the free movement of persons within the member states of the European Community brought with it questions of social security, e.g. with regard to migrant workers. The Institute also did pioneering work in this area. As a result, the theoretical foundation of conflict and coordination law in the context of social law was laid in the 1980s.

The internationally oriented research work at the Institute was enriched by cooperation with academics from all over the world, including quite a few from Eastern Europe, which was still something special during the era before the end of the Cold War. Over the years, this led to a lively scientific exchange across national borders. To this day, the Institute has a worldwide network of correspondents. In addition, the Institute pursued an interdisciplinary approach early on and integrated other social sciences such as economics, sociology, political science, history and ethnology into its research in order to be able to gain a holistic view of law as such.

In his years as director of the Institute, Zacher had thus laid a solid foundation for comparative social law in Germany, which his successor, Prof. Dr. Bernd Baron von Maydell, was able to build on.