Jeremias Kägi graduated in medicine at the University of Zurich in 1956. He received postdoctoral training in biophysical chemistry at Harvard Medical School in Boston and at Carlsberg Laboratory in Copenhagen. He was assistant professor at Harvard Medical School from 1964 to 1969. Thereafter he was appointed Professor of Biochemistry at the University of Zurich. From 1973 to 1991, he acted as co-director and from 1991 to 1997 as director of the Department of Biochemistry. During his tenure, the Department reorganized its teaching program for medical students and extended its biochemistry curriculum to the Faculty of Science. J. Kägi contributed significantly to the development of the department into an internationally acknowledged research center of biochemistry.
His research on the structure of enzymes by isotope exchange studies gave early indications for function-related flexibility of proteins. He is best known, however, for his studies on the structural characterization and the function and evolution of the ubiquitous metal-storage protein metallothionein.