Born in Hohenems, in the Austrian Alps, Klien decided to start karting and decided to become a Formula One driver after meeting Brazilian F1 driver Ayrton Senna at a race. From 1996 to 1998, Klien won several kart races in both Switzerland and Austria, becoming the Suisse champion in his first year. In 1999, Klien moved to racing in the Formula BMW ADAC Junior Cup, winning four races and finishing fourth in the series. The following year, he moved into the main Formula BMW ADAC Championship with Team Rosberg, finishing the series ranked tenth overall and third in the rookie rankings. Continuing in the series in 2001, Klien managed to win five races, and ended up third in the series. Joining JD Motorsport for the Italian winter Formula Renault series, he won one event, leading to a drive for the team in German Formula Renault for 2002. Klien won four races, winning the German title, and finishing fifth in the European series. From there, Klien moved into the Formula 3 Euroseries, with Mucke Motorsport, winning four races and finishing runner-up in the title to 2004 Toyota F1 test driver Ryan Briscoe. Klien also won the 2003 Marlboro Masters event at Zandvoort. Thanks to financial support from Red Bull, Klien was signed as a race driver for the Jaguar Racing Formula One team in 2004. He had significant pressure on him as second driver to the highly-rated Mark Webber, but was the first driver to outqualify Webber in the same team, and showed impressive speed and ability. At the Belgian Grand Prix, Klien finished in sixth place, scoring three valuable championship points. He finished the season in 16th position. During winter testing in 2005, Klien tested several times for Red Bull Racing alongside Vitantonio Liuzzi and David Coulthard. Klien secured the second race seat at Red Bull, alongside the veteran Coulthard. Klien started the year impressively, scoring points in the first two races before retiring early in the Bahrain Grand Prix. He has since added two further 8th place finishes, a strong 5th in the season-closing Chinese Grand Prix, also qualifying an excellent 6th for the Brazilian Grand Prix. With both Klien and Liuzzi signed to race for the Red Bull team in 2005, Red Bull announced that Liuzzi would be racing in the San Marino, Spanish, Monaco and European Grands Prix in place of Klien. Klien returned to the race seat for the Canadian Grand Prix, expecting to have to hand it back to Liuzzi within a few races. Klien's has maintained the race seat since due to his strong perfomances and Red Bull's purchase of the Minardi team giving them more race seats to share between their drivers for 2006. Red Bull have provision to run a third test driver on the Friday of race weekends; initially Klien was ineligible to do this during Liuzzi's time in the race seat, as he had competed in more than six Grands Prix in the previous two years. On April 14 2005, the FIA received unanimous support from all other teams to delete this rule, and so Klien will be able to function as test driver at the San Marino, Spain, Monaco and European Grand Prix. If this rule change had been rejected, Scott Speed or Neel Jani could have filled the role of third driver for these races. After a promising end of season performance in China, it was confirmed on December 16th that Klien would drive for the Redbull Racing outfit alongside David Coulthard for the 2006 season.