One of the strongest racers from his country, Jarek Janis participated in his first ever race on the 7th of September, in 1991. It was a kart race held in Ceska Lipa. From then on, till the year 1998 Janis won the International championship an impressive eight times.
In 2000 Janis shifted to Formula Palmer Audi, and in the Winter Series, he managed a third place finish. The next year, Janis participated in the European Le Mans championship, with the Lanesra Racing team and finished in third place once again. In 2001, Janis was also the test driver for Formula One team Prost Acer, which was a major achievement.
2002 saw Janis make his Euro 3000 Series debut, where after 2 race wins, he finished in third place overall. Once again Janis got the opportunity to be a test driver in the Formula One, but this time with team F1 Jordan Ford.
In 2004, Janis moved into the Champ Car World Series, and was the first Czech to ever do so. He was with Dale Coyne Racing team and participated in one race in Australia. He also appeared in test sessions for Forsythe Racing team. The same year Janis was crowned DTM champion, where he participated with the Mercedes Junior team.
In 2005, Janis appeared in the International championship of the Czech Republic in a Mercedes Benz CLK AMG DTM, and grabbed top honors in the 6 Hours Endurance race. In the same year Janis came second in the Italia championship and the very next year he participated in the FIA GT, with Zakspeed team and finished third overall. He also grabbed the Best Driver Award.