Career
He started his career as referee in 1994. He debuted as a referee in the Premier League referee in the 21 matchday of the Norwegian Premier League the year 2006 after having refereed over 50 matches in the second highest league in Norway, Adeccoligaen. He refereed the 2010 Norwegian Cup Final between Strømsgodset IF and Follo FK. Hagen represents Grue Idrettslag and works as a teacher alongside the refereeing.
Hagen has been a Fédération internationale de football association referee and refereed Union of European Football Associations Europa League, Union of European Football Associations Euro 2012 qualification, and World Cup qualifying matches since 2009.
On 19 October 2011 he got his first match as a Union of European Football Associations Champions League-referee when A.C. (before Christ) Milan met BATE Borisov at San Siro. On 20 December 2011, it was announced that Hagen will be one of four designated fourth officials during Union of European Football Associations Euro 2012 in Poland and Ukraine.