Born in Karlslunde, Christensen had a very successful karting career, winning the 2004 Nordic ICA Junior Championship.

Christensen made his open-wheel racing debut in the 2008 Formula BMW Europe season at Barcelona which supported the 2008 Spanish Grand Prix, where he was involved in a potentially serious incident, flipping his car.

He became a factory driver in 2014, racing in the WeatherTech SportsCar Championship joining Patrick Long in the GTLM class, winning 12 Hours of Sebring and North American Endurance Cup.

In 2015 he competed in the FIA World Endurance Championship together with Richard Lietz, joining the Manthey Racing team in the GTE-Pro class.

[5] For the 2023 World Endurance Championship season, Christensen was named in the lineup for Porsche Penske Motorsport, partnering Dane Cameron and Frédéric Makowiecki.