Xavier Siméon becomes Belgian Champion in karting in 1998. He then makes his debuts in motorcycle racing. In 2005 he competes in the European Superstock 600 Championship. He wins the European title in 2006. In 2007 he starts in the Superstock 1000 championship. In 2008 he wins the junior title by finishing fourth in the championship. In 2009, he wins the FIM Superstock 1000 Championship with Ducati.
Xavier Siméon then decides to enter the Moto2 Championship with the Holiday Gym team. He is number 19 and is the first Belgian representative in Motorcycle Grand Prix since Sébastien Le Grelle. He competes in ten races of the 2010 season and is ranked eighth in the British Grand Prix. In 2011, Xavier Siméon enters the Tech 3 RTL SPORT team. He re-signs for the 2012 season with the same French Tech3 team.
2013 sees a new start for Xavier who joins the Spanish team “Stop and Go” (SAG) on a Kalex, and starts to be managed by ZELOS, company launched by Freddy Tacheny.At the French Grand Prix, Simeon becomes the first Belgian rider since Didier de Radiguès in 1990 to take a podium finish. Later in the season, Siméon took pole position for the German Grand Prix, the first such result for a Belgian since de Radiguès in 1989. He finishes 12th in the Moto2 World Championship. Xavier Siméon signs for the 2014 season with the team Federal Oil/Gresini Racing. He earns his best Moto2 result with a 2nd place finish at the Rio Hondo Termas in Argentina. The 2015 season kicks off with Simeon finishing second at the opening GP in Qatar. Regularly in the top 10, Xavier won the 1st Grand Prix of his career on July 12 on the German circuit of Sachsenring and closed his season to a meritorious 7th place in the championship.
For 2016 Xavier signs with QMMF to race a Speed Up y and in 2017 gets ack on a Kalex bike with Tasca Racing, but both seasons were difficult and he struggled to achieve the expected results.
2018 is a big year for Xavier Simeon as he debuts in MotoGP with Reale Avintia Racing and riding a Ducati Desmosedici GP16. His winter testing has been good and Xavi is ready to start his first MotoGP season, but he knows that this will be a year were he will need to give his maximum to learn all the secrets of the premier class.