The Keplergebäude building contains a number of classrooms, professors' offices, some institutes, subject-area libraries, and the offices of the Austrian National Union of Students (ÖH). Prospective students and enrolled students can find student representative offices, the Austrian student union's social office, the Austrian student union bookstore and book exchange. There are also offices for students who have a migration background and for students studying abroad at the JKU for a semester or a year. The Ch@t-Café is a popular meeting place for students and faculty members alike, serving up quick refreshments and coffee specialties.

The Keplergebäude building can also hold large events, such as career fairs and study information fairs. One of Upper Austria's largest study fairs, the SIM, takes place here on campus every fall.

Kepler's astronomy book Harmonice mundi focuses on a "harmonic law". Kepler believed that God perpetuated a kind of harmony in the solar system and that each planet has a melody in harmony with other planets. "I feel seized by an inexpressible rapture because of the divine spectacle of celestial harmony. For we see here how God, like a human master builder, according to order and rule, has approached the foundation of the world." Kepler's views corresponded to what is today referred to as the anthropic principle. Another manuscript described a compilation of correspondence between the Bible and scientific facts. He was unable to publish this essay due to increasing pressure by the Church.