Heidfeld began competitive karting at age eleven and moved to German Formula Ford in 1994, winning eight of nine races in his debut season. He reached the German Formula Three Championship in 1996, finishing third before taking the title outright in 1997 for Bertram Schäfer Racing with McLaren/West backing, including victory at the Monaco Grand Prix Formula Three support race. That same year, competing at the Macau Grand Prix, he won the first heat of the race, which drew the attention of Mercedes motorsport chief Norbert Haug and set the foundation for his McLaren test-driver relationship.
In International Formula 3000 he finished runner-up to Juan Pablo Montoya in 1998 — losing the championship by seven points after being demoted to the back of the grid at the final race due to non-compliant fuel — then won the series outright in 1999.
Heidfeld made his Formula One debut with Prost Grand Prix in 2000 alongside Jean Alesi, but the team's AP03 was uncompetitive and he scored no championship points. He moved to Sauber in 2001, where he outscored rookie teammate Kimi Räikkönen and took his maiden podium with third place at the Brazilian Grand Prix. Despite outperforming Räikkönen over the season, the McLaren seat vacated by Mika Häkkinen went to the Finn rather than Heidfeld.
He remained at Sauber through 2003, then moved to Jordan in 2004, extracting solid results from the uncompetitive EJ14. A move to Williams in 2005 yielded three podiums and his sole career pole position at the European Grand Prix, but a testing accident and a cycling injury cost him the Italian, Belgian, and Brazilian Grands Prix.
Heidfeld joined BMW Sauber for 2006 when BMW bought the team, staying for four seasons. He scored eight podiums in that period and finished a career-best fifth in the 2007 World Drivers' Championship with 61 points, outscoring teammate Robert Kubica by 22 points. He also finished second behind Kubica at the 2008 Canadian Grand Prix — the team's first and only one-two — despite having potentially the faster race pace. His remarkable consistency in 2008 saw him become only the second driver in the sport's history to complete all eighteen races of a single season.
After BMW's withdrawal at the end of 2009, Heidfeld served as a Mercedes test driver before replacing Pedro de la Rosa at Sauber mid-season in 2010. In 2011 he substituted for the injured Robert Kubica at Renault, taking a podium in Malaysia to break Stefan Johansson's then-record of twelve podiums without a win, before being replaced by Bruno Senna after the Hungarian Grand Prix.
Following his Formula One exit, Heidfeld raced for Rebellion Racing in the FIA World Endurance Championship from 2012, finishing fourth overall at Le Mans in 2012 and winning the LMP1-L class there in 2014. He also finished runner-up in the 2013 American Le Mans Series.
Heidfeld signed for Venturi in the inaugural 2014-15 Formula E season. He competed for three seasons total, moving to Mahindra in 2015 and accumulating eight podiums across his Formula E career before departing at the end of 2017-18.
Nick Heidfeld's career is defined by consistent pace rarely matched by results. His 13 Formula One podiums without a race win remains the all-time record for the sport, earning him the nickname "Quick Nick" — coined during his 2005 Williams season. An academic ranking study published in 2016 placed him 23rd among all Formula One drivers of all time when machine performance was factored out. He was also chairman of the Grand Prix Drivers' Association in 2010.