Berthon began his international karting career in 2006, with the highlights being a third-place finish in the Copa Campeones Trophy ICA class and fifth in the French Championship Elite category.

He won his first Eurocup race at the opening round in Barcelona after teammate Albert Costa was disqualified for a technical infringement.

[6] He drove for the recently–crowned champions Draco Racing during the next test at the Circuit de Catalunya and in December 2009 it was announced that he would drive for the team in the 2010 season.

[8] After finishing on the podium at the season–opener in Motorland Aragón and again at Brno, Berthon secured his first Formula Renault 3.5 Series win on home soil at Magny–Cours, holding off a stiff challenge from Tech 1 Racing's Daniel Ricciardo.

[10] Berthon returned to the series in 2011, replacing Dean Stoneman at ISR Racing after the Briton was forced to pull out of the championship due to illness.

Berthon made his debut in the GP2 Asia Series in 2011, partnering Spaniard Dani Clos at the Racing Engineering team.

In the winter of 2012 prior to the start of the GP2 season, Berthon travelled to New Zealand to compete in the five-round Toyota Racing Series in a grid which featured a mix of local and foreign drivers.