In January 2012, Istok Rodeš took part in the 2012 Winter Youth Olympic Games and, in addition to a sixth place in giant slalom, achieved two ninth places in slalom and super combined . A year later he made his World Cup debut in slalom on Sljeme . At the 2013 World Championships in Schladming , he started in the Super-G and finished 62nd. After that, he mainly competed in the Nor-Am Cup and FIS races . At the 2015 World Championships in Vail / Beaver Creek , he started in Downhill, Super-G and Combined, with a 36th place in combined remaining his best result. In his third Junior World Championship , he achieved his first major successes in March 2016. In the combination he won the bronze medal and in slalom he became the first Croatian junior world champion in history. Two weeks later he finished 17th in the slalom at the World Cup finals in St. Moritz . He won his first World Cup points on January 8, 2017, finishing 25th in the Adelboden slalom . He finished the world championship in St. Moritz with a 30th slalom rank. In the following winter he only competed sporadically in World Cup slaloms, but was never able to qualify for the second round. At the 2018 Winter Olympics in Pyeongchang , he achieved his best result in a major event in slalom with 21st place.
In December 2018 he achieved his first top 10 result in the World Cup with seventh place in the slalom of Madonna di Campiglio . Just two weeks later he was able to confirm this performance with the same result in the home race on Sljeme. In the 2018/19 season, he won the slalom classification of the European Cup.