He began his motorsport career in 1997 at age 15. He has won several karting championships as well as the BMW ADAC Formula Junior Cup in 2000 and the BMW ADAC Formula Championship in 2001.
In his first International German Formula 3 season in 2002, he finished third in the standings en route to rookie of the year honors. In 2003, he competed in the European Formula 3 Championship, winning three races and scoring three other podium finishes, which were enough to place him in fifth position in the Championship.
He began 2004 as Jordan's Friday test driver, where he continually outshone the team's race driver Giorgio Pantano. He stood in for Pantano when he had a contract dispute with the team at the Canadian Grand Prix. He beat his team-mate Nick Heidfield to finish eleventh. However when Toyota and Williams were disqualified for technical infringements Timo and Nick moved up into the points, thus joining a select group of drivers who have scored a World Championship point in their first Formula One race. He returned to his customary Friday role for the next few races, until Pantano's money finally ran out before China and Tim O'Glock, as he was known by the Irish team, took over for the last three races. He looked in line for a full-time seat in 2005 until the team was bought by Russian tycoon Alex Schnaider.
Glock thus switched his attention to America in 2005 and signed a contract to race in Champ Cars with Paul Gentilozzi's Rocketsports team. His best finish of the year was a second place finish at the Circuit Gilles Villeneuve in Montreal on August 28, where he was defeated by Oriol Servia. In the closing laps of the race Glock twice managed to retain the lead over Servia by missing the track's final chicane. As the rules require drivers who blatantly gain or retain a position by driving off the racing surface to give way, Timo was asked to move over by Champ Car officials and let Servia take the lead. Timo obliged midway through the final lap, giving him enough time to try and take the lead back, but to no avail. Glock went on to finish 8th in the final season points standings and win Champ Car World Series Rookie of the Year honors.
In 2006, Glock raced in the GP2 Series. He started the series with the midfield BCN Competicion team, gaining average results. However, a mid-season move to the front-running iSport team proved conducive and after a series of impressive results he finished 4th in the final classification of the Driver standings, leading to his re-signing for 2007 by the team.
That year he tested a F1 car again, this time for BMW Sauber, which led to him being signed as the team's second test driver for 2007. Following the serious crash of regular BMW driver Robert Kubica in Canada, it was speculated that Glock could take over the drive. However, the team chose Sebastian Vettel to substitute instead.
After 5 rounds he had finished on the podium 5 times and led the Championship by 16 points. However after taking pole for the round at Magny Cours he clashed with Andi Zuber at the start. They banged wheels and Zuber was launched up and over his Glock's car, with the German lucky to escape injury as the bottom of the chassis narrowly missed his head. His lead has thus been cut to 8 points going into the Silverstone race.