Lewen competed at the 2010 Winter Olympics for Sweden. He placed 19th in the qualifying round in ski cross, to advance to the knockout stages. In the first round, he finished 4th in his heat, and did not advance.
Lewen made his World Cup debut in November 2002. As of March 2013, he has ten World Cup podiums and five victories, with the first coming in 2007/08 at Grindelwald. His best World Cup overall finish in ski cross is 2nd, in 2007/08.