Kleen qualified as a crew member for the German squad in the Star class at the 2012 Summer Olympics in London by placing second and receiving a berth from the ISAF World Championships in Perth, Western Australia. Teaming with his partner Robert Stanjek in the opening series, the German duo recorded a net score of 70 points throughout the entire race, but came up short for the medal podium with a satisfying sixth position against a fleet of sixteen boats.