Klaus Katzur started swimming at the age of 14, but seriously commenced competitive sports in 1963. Two years later he beat the previous top East German breaststroker, Egon Henninger, for the first time to become national champion in the 200 m breaststroke. He won additional titles at 100 m (1967, 1971 and 1972) and 200 m (1967, 1969 and 1972) breaststroke and the 400 m individual medley in 1965. In 1966 Katzur won his first international medal as bronze medalist in the 400 IM at the European Championships. In 1972 he achieved his greatest individual success winning the 200 m breaststroke at the European Championships. At the same event he won his second title in the medley relay. Katzur competed in three Olympics but took his only medal in 1972 as a silver medalist with the GDR medley relay. In 1964, he was a member of the mixed German team, and in 1968 he also represented former GDR.
After his active career Katzur took over the care of the youth section of ASK Potsdam. In 1987 he became a functionary of the figure skating section of SC Karl-Marx-Stadt (now Chemnitz). After German reunification he worked as a pool manager and coach in Würzburg, and he later sold fixtures and fittings for gyms. In 2000 Katzur became chairman of the Association of German Olympians and a personal member of the German NOC. Only two years later he was confronted with allegations of having cooperated with the GDR’s Stasi (secret police). Katzur was married for a time to double gold medalist Petra Thümer but they later divorced.