Leclerc began his karting career in 2005, winning the French PACA Championship in 2005, 2006 and 2008. In 2009 he became French Cadet champion before moving up to the KF3 class in 2010, where he won the Junior Monaco Kart Cup. He continued in the KF3 class for 2011, winning the CIK-FIA KF3 World Cup, the CIK-FIA Karting Academy Trophy and the ERDF Junior Kart Masters. During the year, Leclerc also became a member of Nicolas Todt’s All Road Management company.

In claiming the championship, Leclerc became the youngest ever champion of the main support series for Formula 1 at 19 years 356 days old, and the first driver since Nico Hülkenberg in 2009 to win the championship in their rookie season (a feat which only Nico Rosberg and Lewis Hamilton have previously accomplished) and is the only driver to claim a championship with the Dallara GP2/11 chassis in their rookie season.

At the first race after the summer break, the Belgian Grand Prix, Leclerc took his third pole position of the season alongside teammate Sebastian Vettel in 2nd—the second Ferrari front row lockout of the season. During the race, Leclerc fended off the charging Mercedes of Lewis Hamilton to record his maiden Grand Prix win, making him the youngest ever Ferrari race winner. After the race he dedicated his maiden victory to his former competitor Anthoine Hubert, who was killed in an accident during the previous day’s Formula 2 feature race at the same circuit. At the Italian Grand Prix, Leclerc won the race from pole position after defending his position from both Mercedes drivers and became the first Ferrari driver to win at Monza since Fernando Alonso won there for the team in 2010. He scored his third consecutive pole in Singapore. Initially leading the race, he finished in second place after he was undercut by teammate Vettel. In Russia, he took his fourth consecutive pole position and his sixth of the season. Vettel passed Leclerc into the first corner and led for the first half of the race, before the team orchestrated an undercut in Leclerc’s favour to let him retake the lead. Vettel retired from the race shortly after with a hybrid system failure, bringing out the virtual safety car. This greatly benefited the Mercedes drivers, who made their pit stops and eventually finished the race ahead of Leclerc in third.

Leclerc graduated to the KF2 category in 2012 with the factory-backed ART Grand Prix team, winning the WSK Euro Series title, as well as finishing runner-up in the CIK-FIA European KF2 Championship and the CIK-FIA Under 18 World Karting Championship. In his final year of karting in 2013, Leclerc won the South Garda Winter Cup and claimed sixth position in the CIK-FIA European KZ Championship and finished second in the CIK-FIA World KZ Championship, behind current Red Bull Formula One driver Max Verstappen.

In 2014, Leclerc graduated to single-seaters, racing in the Formula Renault 2.0 Alps championship for British team Fortec Motorsports. During the season, he took seven podium positions, including a double victory at Monza, to finish runner-up in the championship behind Koiranen GP’s Nyck de Vries. Leclerc also won the Junior Championship title at the final race of the season in Jerez, finishing ahead of Russian teenager Matevos Isaakyan.

In Austria he took his fifth pole position, and then won the feature race from pole despite coming under pressure from teammate Fuoco, and towards the end, the DAMS of Latifi. He would retire from the sprint race after colliding with Fuoco and spinning out. By taking pole for the sixth time for the next race, at Silverstone, he matched the record for most pole positions in a row, which was set by Stoffel Vandoorne in 2014 and 2015, when the series were called GP2 Series. He won the feature race, even after his car set alight during the race, and even after one of his wing mirrors detached in the closing stages.

Leclerc graduated to Formula Three in 2015, racing in the FIA Formula 3 European Championship with Dutch team Van Amersfoort Racing. At the opening round of the season in Silverstone, Leclerc inherited pole position for the second and third races of the weekend after original pole-sitter Felix Rosenqvist was excluded for a technical infringement. He went on to take his first race victory in the third race of the weekend, ahead of Antonio Giovinazzi and Jake Dennis. He took his second victory at the following round in Hockenheim, winning the third race as well as taking two additional podiums and three rookie victories over the course of the event. Leclerc scored his third win in the first race at Spa-Francorchamps which saw him take the lead in the championship. However, Leclerc finished fourth in the standings, mostly due to damage sustained to his car’s chassis following a collision with Lance Stroll at Zandvoort.

In November 2015, Leclerc finished second at the Macau Grand Prix.

In December 2015, Leclerc partook in post-season testing with ART Grand Prix and Arden International. In February 2016, de Vries confirmed that Leclerc would race in the 2016 season. ART signed Leclerc the following week. With the team, he claimed three victories and took the title in Abu Dhabi, despite crashing out in the feature race.

In 2016, Leclerc joined the Ferrari Driver Academy and he acted as development driver for Haas F1 Team and Scuderia Ferrari. As part of his role as development driver, Leclerc participated in the first practice session of the British and German Grands Prix driving for Haas. It was believed that if Leclerc won the GP3 Series championship, he would follow Daniil Kvyat and Valtteri Bottas direct from GP3 into F1 with Haas. However this was debunked by Haas team principal Guenther Steiner who said that Leclerc would progress to the 2017 FIA Formula 2 Championship.

In 2017, he took part in the mid-season Hungaroring test following the Hungarian Grand Prix, driving the Ferrari SF70H. He was fastest on the first day of the test, running 98 laps in the process and he did not take part in the second day’s test. Kimi Räikkönen also praised Leclerc saying “It’s not easy to do well in a different car from what you normally drive. But Leclerc has shown great progress, and for sure he will do great things in the future”.

For the 2018 Formula One World Championship, Leclerc signed for the Sauber F1 Team as a race driver, replacing Pascal Wehrlein and alongside Marcus Ericsson. This marked the first appearance of a Monégasque Formula One driver since Olivier Beretta in 1994. At the Azerbaijan Grand Prix, a sixth-place finish saw him become the second Monégasque driver to score points in Formula One after Louis Chiron, who finished third at the 1950 Monaco Grand Prix. At his first home race in Formula One, Leclerc suffered a brake failure in the closing laps, colliding into the back of Brendon Hartley and forcing both cars into retirement. Three consecutive points finishes followed before a run of five races without points. This run included three retirements; a loose wheel in Britain, suspension damage after colliding with Sergio Pérez in Hungary, and a multi-car accident in Belgium caused by Nico Hülkenberg which resulted in Fernando Alonso being launched over the top of Leclerc’s car.

Scuderia Ferrari signed Leclerc for the 2019 season, replacing 2007 World Champion Kimi Räikkönen, who took his place at Sauber (now Alfa Romeo). While initially only announced for 2019, a few days later, then-Ferrari team principal Maurizio Arrivabene indicated that Leclerc’s contract was going to be four seasons long, running “at least until 2022.” Leclerc made his first test day as an official Ferrari race driver in November 2018 during the end of season test.

During his childhood, Leclerc was a friend of the late Jules Bianchi from nearby Nice, who won his first racing championship when Leclerc was ten years old. Leclerc began karting at the track managed by Bianchi’s father in Brignoles. Like Bianchi, Leclerc joined the ARM management company headed by Nicolas Todt. In an interview in 2018, Leclerc revealed that Bianchi was also his godfather.

At the 2020 Italian Grand Prix he qualified thirteenth but in the race he crashed out at Parabolica on lap 24, while he was in fourth, thanks to a pitstop earlier than others who pitted during a Safety Car period. The crash caused a red flag.

Leclerc made his film debut in a remake of the 1976 French short film C’etait un rendez-vous. This version, entitled Le Grand Rendez-vous, is set on the Circuit de Monaco instead of the streets of Paris where the 1976 original was set. The car featured in the film was a Ferrari SF90 Stradale. The film was released on 13 June 2020.

On 13–14 June 2020, Leclerc teamed up alongside fellow Formula One driver Antonio Giovinazzi as well as esports racers David Tonizza and Enzo Bonito in a Virtual 24 Hours of Le Mans race on rFactor 2 driving a GTE Spec Ferrari 488 GTE for AF Corse. They competed against other Formula One drivers in the event such as: Felipe Massa, Giancarlo Fisichella, Pierre Gasly, Lando Norris, Max Verstappen, Juan Pablo Montoya, Rubens Barrichello, Jan Magnussen, Jean-Éric Vergne, Sebastian Buemi, Stoffel Vandoorne and Fernando Alonso. The race was organised after the coronavirus pandemic forced the real life 2020 24 Hours of Le Mans to be postponed until September. The race for Giovinazzi, Bonito, Tonizza and Leclerc was blighted by technical problems one of which led Leclerc to spinning off at a time when he had been running in a solid second place in the GTE class. The quartet eventually finished 18th in the GTE class in a race won in class by Porsche Esports Team and overall by Rebellion Williams Racing.

Prior to competing in the 70th Anniversary Grand Prix in 2020 at Silverstone, Leclerc reacted angrily to accusations that he was racist and opposed to the Black Lives Matter movement, responding by saying racism is “disgusting” and accusing headlines of attempting to manipulate his words. The accusations came after he was one of six drivers who opted not to take a knee during the pre race ceremonies of the opening events of the 2020 Formula One World Championship as part of the sports anti-racism campaign. He stated that he chose not to take a knee due to the negative political connotations he felt such a gesture could have.