Whilst training as a mechanic Jaroslav Nikodým took up judo when he was 15-years-old, competing at a club in the northern Czechoslovak town of Rumburk. Nikodým then moved to the city of Jihlava to continue his judo, but he was forced to drop the sport briefly due to military service, including fighting during the Warsaw Pact invasion of Czechoslovakia. By then working as a locksmith at an engineering firm, Nikodým returned to competing in judo competitions for Spartak ZVÚ Hradec Králové, becoming a multiple-time national champion. In 1978 he joined the national judo team as a light-heavyweight, finishing fifth at the European Championships in both 1979 and 1980. His performances earned Nikodým a place on the Olympic team for the Moskva Games, but he lost his opening bout to Mark Chittenden (GBR) in just 12 seconds.