Lovro Radonić was a footballer prior to World War II, but after the conflict he took up a more lasting interest in aquatics and, in particular, water polo. He débuted at the Summer Olympics in 1952 as a member of the Yugoslavian team that took home silver after losing the final match to the Hungarians. Yugoslavia, with Radonić, repeated this feat in 1956 and Radonić made one more appearance at the Games in 1960, when he was eliminated in the opening heats of the 200 metre butterfly event. He was also a member of the Yugoslavian teams that took silver at the 1954 and 1958 European Championships and bronze in 1950. Additionally, he was the oldest player on the Yugoslavian squad that captured gold at the 1959 Mediterranean Games. At the national level he won five water polo titles in 1952, 1953, 1955, 1956, and 1961. He retired from active competition in 1964, but then spent four years as a coach in the second tier of Yugoslavian water polo.