He came from a very old Czech theatrical family of Steimar and artistic family of Kodet, he was the son of Czech actress Jiřina Steimar and sculptor Jan Kodet. After her parents divorced, her mother married Jaroslav Juhan, a car racer, but he emigrated. This had an impact on the further studies of Jiří Kodet, who was expelled from the grammar school and was not admitted to the DAMU until the second time.

He left the DAMU before graduating and began his theatre career at the East Bohemian Theatre in Pardubice (1961-1962). In 1962-64 he was in the Artistic Military Ensemble, based in Pohořelec, Prague. With this ensemble he toured a large part of the former Czechoslovakia. His future colleagues from the Drama Club, Jiří Hrzán, Jiří Zahajský and Petr Skoumal, were in the ensemble with him. In Pardubice, he was sought out by Jan Kačer, who was assembling a troupe for the Petr Bezruč Theatre in Ostrava. Kodet worked in Ostrava from 1963-1965, and from 1966 he played at the Prague Drama Club, where some of the members of the Ostrava ensemble moved. In 1991 he became a member of the drama company of the National Theatre in Prague.

During his lifetime he played a number of small and episodic roles in film and television, but it was not until the end of his life that he was able to play major roles, mainly thanks to director Jan Hřebejk, who cast him in his film Divided We Fall, and earlier also in Cosy Dens, which was his most successful film ever.Jiří Kodet, licensed under CC-BY-SA, full list of contributors on Wikipedia.