Buemi started karting in 1998 where he took his first win at the 1998 Mini Swiss Championship with 152 points. He also took karting wins in the 1999 Mini 90 KIA Cup and the 1999 Mini 90 Swiss Championship. 2002 was a strong year for him in regards to karting as he placed as runner up in both the ICA Junior 13 degrees Trofeo Andrea Margutti and the ICA Junior Monaco Kart Cup. He also took the championship in the ICA Junior European Championship. In his final karting year, he took two more wins in the 2003 ICA Junior Western Region Qualification European Championship with Intrepid Kart Technology and the ICA Junior Italian Open Masters.
Sébastien graduated to single seaters in 2004 where he joined Lars Kaufmann Motorsport in the Formula BMW ADAC to take 188 points and 3rd in the championship. He stuck in the championship for a second year but moved to ADAC Berlin-Brandenburg e.V. where he took 282 points and finished second in the standings. He managed to win seven out of his twenty races with 9 other podiums. Buemi also joined ASL Team Mücke Motorsport for the Formula BMW World Final where he also took second. He also debuted in Formula 3 when he joined Racing Engineering for a single race in the F3 Spain Series.
He kept busy in 2006 when he raced full time with Mücke Motorsport in the Formula 3 Euro Series where he managed one win,.three podiums and six fastest laps where he finished 11th in the standings. Alongside his full season, he spent eight races with Motopark Academy in the Formula Renault 2.0 NEC Championship where he took 6 podiums with 2 wins to place him seventh in the standings. He also spent 6 races in the Formula Renault 2.0 Eurocup with Motopark to take a single win and 11th in the standings. For single races, Buemi competed with Carlin Motorsport in the 53rd Polytec Macau Formula 3 Grand Prix where he finished 4th and the Masters of Formula 3 with ASL Team Mücke Motorsport where he finished 3rd. Between 2006 and 2007, he raced with Team Switzerland in the A1GP for 12 races but didn’t manage to take a single podium yet still finished 8th with 50 points. Leading into 2007, he returned to the Polytec Formula 3 Macau Grand Prix with Räikkönen Robertson Racing where he finished 11th. Buemi also returned to the Formula 3 Euro Series with ASL-Team Mücke Motorsport where he took 10 podiums and 3 more wins where he racked up 95 points and 2nd in the standings. He also debuted in the GP2 Series with ART Grand Prix for 11 races, taking 6 points and 21st in the championship. Buemi returned to GP2 for a second year where he joined Trust Team Arden to take 50 points and 6th in the standings. He also competed with the team at the GP2 Asia Series where he took five podiums of which 1 was a win and placed himself second in the standings.
2012 marked the year that Buemi made his debut in endurance racing. He joined Toyota Racing in the FIA World Endurance Championship and the 24 Hours of Le Mans Series. He also joined Boutsen Ginion Racing in the European Le Mans Series. He stuck with it in 2013 and finished 3rd in the FIA World Endurance Championship and 2nd in the 24 Hours of Le Mans with Toyota Racing. He stuck with the team for a third year and managed to win the FIA World Endurance Championship and place 3rd in the 24 Hours of Le Mans. He managed seven podiums in the Endurance Championship of which four were wins. Buemi raced with the team in both championships from 2015 to 2017 which his best finishes being second in the FIA World Endurance Championship in 2017.
Buemi stuck with Toyota for the 24 Hours of Le Mans in 2018 and 2019 where he took first in both championships. He also raced with the team between 2018 and 2019 in the FIA World Endurance where he also finished first. He currently still races with the team in the FIA World Endurance Championship between 2019 and 2020 where after five races, he sits at 2nd in the standings with 5 podiums, of which one is a win, and 107 points.
Sébastien debuted as a Formula One Test Driver with Red Bull Racing in 2007 and in 2008 before moving to Formula One in 2009 through until 2011. He took 16th in his first two years with 6 and 8 points, followed by 15th with 15 points. He returned to being a test driver for Red Bull Racing in 2012 which he continued until 2015. Buemi made the switch to a reserve driver as of 2016 and still remains in 2020.
Buemi made his debut in the FIA Formula E Championship in 2014/15 with Renault e.dams for eleven races where he took 5 podiums with three wins to take 143 points and second in the standings. He stuck with the team for the 2015 to 2016 to take the title for the second season of FE with 155 points and 6 podiums of which half were wins. In his third year, he stayed with the team for the 2016- 2017 season where he took 6 wins. These were his only podiums for the year but it took him to second in the championship with 157 points. His year dipped in the 2017 to 2018 season as he finished 4th in the standings with 125 points after taking four podiums but not managing to take a win.
In the 2018 to 2019 series, the team made the name change to Nissan e.dams and took Buemi with them for his fifth year. Out of 13 races, he took 4 podiums and a single win to take 119 points for the team and a second place finish in the standings.