Glock began motorsport in 1998 at the age of 15. He won the BMW ADAC Formula Junior Cup in 2000, the Formula BMW ADAC Championship in 2001, and finished third in his debut German Formula Three season in 2002, earning Rookie of the Year honours. In 2003, he contested the Formula Three Euroseries, winning three races and securing three further podiums to place fifth in the championship.
Glock joined Jordan Grand Prix as a test driver for 2004 and made his Formula One race debut at the Canadian Grand Prix as a replacement for Giorgio Pantano, who had entered a contract dispute with the team. Glock finished what appeared to be eleventh but inherited seventh place following post-race disqualifications of the Williams and Toyota cars, scoring two championship points on his debut. He remained with Jordan for the final three races of the season as Pantano's replacement.
In 2005, Glock moved to the United States to race in the Champ Car World Series with Paul Gentilozzi's Rocketsports team. His best result was second place at the Circuit Gilles Villeneuve in Montreal, where he was directed to cede a position he had retained by cutting the track's final chicane. He finished eighth in the final standings and won the series' Rookie of the Year award.
Glock entered the GP2 Series in 2006 with the midfield BCN Competicion team but moved mid-season to the front-running iSport International outfit. His results improved markedly and he finished fourth in the championship, earning the series' most-improved-driver award. Alongside his GP2 duties he tested for BMW Sauber, which led to him signing as the team's second test driver for 2007.
Returning to iSport for 2007, Glock won one feature race and four sprint races across the season to claim the GP2 championship. Following the serious crash of BMW race driver Robert Kubica in Canada, there was speculation Glock might be elevated to the race seat, but the team chose test driver Sebastian Vettel instead. Glock was subsequently promoted to BMW's main test and reserve driver role.
Glock signed a three-year contract with Toyota for 2008, a deal that required resolution through the Contract Recognition Board after BMW contested his commitment. He scored his first points with Toyota at the Canadian Grand Prix, finishing fourth. At the Hungarian Grand Prix he qualified a career-best fifth and finished second.
His most discussed moment came at the 2008 Brazilian Grand Prix. Running in the final stages on dry-weather tyres while rain fell, Glock was overtaken by Lewis Hamilton and Sebastian Vettel in the closing corners of the final lap. Hamilton's pass for fifth place gave him the championship by one point ahead of Felipe Massa, who had won the race. Glock and his team required a police escort out of the country due to the reaction from Massa's supporters. The incident and commentator Martin Brundle's live exclamation of "Is that Glock going slowly?" became widely circulated in motor racing circles.
In 2009 Glock finished third at a rain-shortened Malaysian Grand Prix and second at the Singapore Grand Prix. He was injured in a heavy crash during qualifying for the Japanese Grand Prix, suffering a cracked vertebra, and missed the Brazilian and Abu Dhabi rounds. Toyota withdrew from Formula One at the end of 2009.
Glock drove for Virgin Racing in 2010 and 2011 and Marussia F1 in 2012, finishing 12th at the Singapore Grand Prix in his final season — a result that helped Marussia secure tenth place in the Constructors' Championship. He left Marussia by mutual consent in January 2013.
Switching to the Deutsche Tourenwagen Masters with BMW, Glock scored his first DTM podium in only his third race and won at the Hockenheimring season finale. He continued in the DTM for multiple seasons, later also working as a Formula One pundit for German broadcaster RTL and subsequently for Sky Sport Germany.
Glock's junior career trajectory — German Formula Three, Formula Three Euroseries, a Formula One taste with Jordan, Champ Car, and then GP2 championship victory — represented an unusually wide path to the top level. The 2008 Brazilian Grand Prix finale remains the moment most associated with his name in Formula One history, though his clean GP2 title and his Toyota podiums demonstrate that his pace was genuine across multiple categories.