Ilona Novák’s swimming career began on the eve of World War II and she won her first national medal, silver in the 100 metres backstroke, in 1939. The following year she won her first of 35 national titles, in a career that lasted until 1956. She made her Olympic début in 1948 in London, where she just missed a medal by coming in fourth in the 100 metres backstroke. She was also fifth in the 4x100 metres freestyle relay with Mária Littomeritzky, Judit Temes, and Éva Székely. At the 1952 Helsinki Olympics, Novák, Temes, Littomeritzky, Katalin Szőke and Ilona’s sister Éva won gold in this event, while Ilona was also eliminated in the semi-finals of the 100 metres freestyle. She competed at the European Championships in 1947 and 1954, but did not reach the podium, although she did help set a world record in the 4x100 metres freestyle in 1952. Following her retirement from competition, she was active as a sports administrator and physical education teacher, serving on the boards of both the Hungarian and European swimming associations.