His personal best throw and Slovenian record is 82.58 metres, achieved in September 2009 in Celje, Slovenia.
On 8 October 2009, Kozmus unexpectedly announced his temporary retirement from athletics. On 25 October 2010, he announced his return. After moderate achievements in the 2011 season, Kozmus stated his goal at the 2011 World Championships in Athletics was to place in the top eight in the finals. Still, he won bronze with 79.39 m.