Jarno Müller began racing minibikes in his native Germany at the age of 7 and within a year finished runner-up in the junior category of the national series. Almost a decade later the youngster contested his first race in the ADAC Junior 125 Cup, where he would lift the title at the third time of asking in 1998 with 5 wins out of 7 races. The following season he took the runner-up spot in the 125 German Championship before going one better in 2000. With simultaneous tenth and seventh placed finishes in the European series to add to his national success, as well as successive wildcard rides at the German Grand Prix, Müller stepped up to the 125 World Championship in 2001 and took four top 15 finishes.