In 2003 he became world champion in the halfpipe at the Snowboard World Championship on Kreischberg . At the 2002 World Cup he was third. In 2006 he became Swiss champion in the halfpipe, in 2002 Swiss champion in freestyle.
On March 14, 2009 Markus Keller won his first World Cup victory. He won the halfpipe event in La Molina in Spain. Thanks to this result, he was finally nominated for the 2010 Winter Olympics in Vancouver . Prior to that, in 2004, with a third place in Kreischberg, he first reached the podium in a World Cup competition.