Mitz, who for Holmens IF is launched, made his international debut at the Junior World Championship 2005 in Finnish Rovaniemi , where he in standalone 36 and with the team, which also includes Fredrik Balkåsen belonged to the 14th and penultimate place reached before the Estonian team. A year later in Kranj, the now 16-year-old competed again in the Junior World Championship and achieved 51st place in the individual and ninth place in the team. From September 2006 he started in the FIS Cup , where he quickly got good placements after a short start-up problem. After he was able to reach 99 points in the FIS Cup 2007/08 and was in 55th place overall, when the FIS Cup took place in Vancouver , he received the nomination for the B team in the Ski Jumping Continental Cup , its jumping took place just one day later on March 1, 2008. Here he managed to place in the points in the first competition with 25th place. After a 30th place in the second competition Mitz had no more opportunities to fight for points and ended the 2007/08 season in 136th place overall. After a transfer back to the FIS Cup in September 2009 and December 2010, he won the team silver medal at the Swedish Championships 2011 in Sollefteå . In January 2012 Mitz got the nomination for the Continental Cup again and from then on he jumped regularly in this series. It took until January 5, 2013 in Zakopane , where Mitz was able to win Continental Cup points again for the first time.
On February 4, 2012 Mitz managed to defeat Carl Nordin , who was favored at the Swedish Championships in 2012 in Örnsköldsvik , who was still leading after the first jump, and thus secured a national team for the first time in his career. He won silver on the large hill behind Nordin.
In March 2013 Mitz started for the last time in an international competition.