Career
Born in Copenhagen, through his youth years, Mortensen has represented several clubs from Copenhagen such as Bachelor of Arts 70, Amager United and the merger-team of several clubs from Amager, Football Club Amager, which changed its name to Amager in the time Mortensen played there. He was signed by Fremad Amager, the flagship of football clubs on Amager in 2006 on his first professional contract. He was spotted by Brøndby scouts in 2007, being signed as a hot new prospect.
However, two years later, he still hadn"t managed to come further than the second team
On December 15, 2009, Mortensen joined Lyngby Boldklub on a three-year deal. Mortensen made his debut for the Denmark Under-21 national team in 2010.