An increasingly large circle of followers, friends and admirers formed around Brunner after the appearance of his 'doctrine of the Spiritual and of the People'. They discussed Brunner's philosophy, but also usually felt strongly attracted by Brunner's personality.

Brunner established closer contact with many of these people, which was reflected in his increasingly extensive correspondence. However, he did not give any lectures or speeches in this circle, nor did he participate in the events of the circle members.

The Brunner circle initially formed in Brunner's immediate surroundings: in 1924, a "Constantin Brunner Gemeinschaft" was founded in Berlin, which organized lectures and publications on Brunner.

As early as 1919, the "Ethical Seminar," founded by Friedrich (Frederick) Kettner, was established in parallel in Czernowitz, where a large group of youth movement members devoted themselves to the study of Brunner's philosophy. The Jewish members of these circles emigrated to many countries in Europe, to the USA, Canada or Israel, where they again formed study circles.

After the war, the survivors founded the Internationaal Constantin Brunner Instituut in The Hague, with the aim of republishing Brunner's writings. Later, a German Brunner Foundation, the Constantin Brunner Foundation in Hamburg, was also established to make Brunner more present in Germany again. For both, see Institutions.

The activities of the Brunner Circle are documented by numerous publications on Brunner (see the complete bibliography), but also by a very extensive correspondence among the members. This correspondence was collected by the ICBI and is now in the Brunner Archives at the Leo Baeck Institute in Berlin. They are accessible online as part of the Constantin Brunner Collection.