Varhaug began his motorsport career in karting in 2005, finishing fifth in the Norwegian Championship ICA Junior category.

[2] At the end of the season, Varhaug took part in Formula Renault 3.5 Series testing at Paul Ricard with the Italian Prema Powerteam, completing over one hundred laps in the process.

[6] Varhaug originally finished in third place in the feature race at Spa–Francorchamps, but was later demoted to 15th after overtaking the safety car.

He finished thirteenth in the Asia series, which along his team-mate's overall victory, allowed DAMS to win the teams' championship.

After losing his GP2 drive at DAMS, Varhaug moved to the Auto GP World Series with the Virtuosi UK team.