Marijan Žužej took up swimming in 1946 and started playing water polo in 1952 after joining HAVK Mladost, playing with them his entire club career. Žužej was called to the Yugoslav national team in 1954 and won silver medals at both the 1954 European Championships and 1956 Olympics. In 1957 Žužej won gold at the Universiade, but at the end of that year suffered a serious car accident that nearly ended his career. He recovered by the 1960 Olympics, where he was fourth with the Yugoslav team, but retired from sports soon thereafter. Žužej later worked as a water polo coach and administrator with his club HAVK Mladost and also worked as an architect in Slovenia and Austria.