His footballing career started Kollmann at his hometown club SC Landskron, his subsequent career took him first to Innsbruck for FC Tirol Innsbruck and after a serious injury, suffered in one of his first games for the Tyrolean FC, soon back to his home to second-rate FC Kärnten where he coached Walter Schachner significantly contributed to the promotion to the top flight in the 2000 /01 season.
After his good performances one was also attracted international attention on him and so he moved in 2001 to the Dutch club Twente Enschede. After two injuries and associated moderate success in the Eredivisie GAK Manager Günther Koschak took the Carinthian already in the following winter break to Graz. But even there, it ran for Kollmann immediately after desire of coach Thijs Libregts he was briefly even banished from the squad. But when his former promoter was hired as a coach with Walter Schachner, celebrated the 1.83 m tall striker his greatest successes so far. He was top scorer in the Austrian T-Mobile Bundesliga and in the same year champion and cup winner with the Athletikern in the season 2003/2004.
After the 2006/ 07 and the turbulence around the GAK season, the striker moved to SK Austria Kärnten. After a year in Carinthia, he returned to the GAK. After he after his return in twelve league inserts scored six goals in the first season and promotion to the First League with his team narrowly failed, he came in the season 2009/10 in 27 league games for use, scoring 25 goals. On 6 December 2011 were announced on the official website GAK that the expiring with the end of 2011 the contract will not be renewed. Kollmann is changed on 12 January 2012 SVG lead castle, a team in the Carinthian league.
Kollmann graduated eleven inserts for the Austrian national team, where he was able to achieve four goals. His international debut he celebrated on 6 September 2003 in the qualifiers for Euro 2004 against the Netherlands. In special memory for his free kick goal for 1:2 connection matches against England ( Full 2:2 ) in qualifying for the 2006 World Cup.