Born in Aalborg, Andreasen started his career as a youth player with AaB but soon moved on to Randers FC where he would have a better chance of making the 1st team. He signed his first professional contract with Randers in summer 2007.[1] Andreasen made his debut for the Randers FC senior squad on 30 March 2008 in a game against AC Horsens. His first goal for the club was a game winner against FC Nordsjælland on 12 May 2008. After the game Randers manager Colin Todd stated that Andreasen had a bright future in front of him, due to his goal scoring ability.[2] On 29 April 2009 Randers announced that they had decided to loan out Andreasen to TPS Turku in the finish Veikkausliiga until the end of the 2008-09 season.[3] Andreasen enjoyed a successful loan spell at TPS, scoring 5 goals in 8 games for the club, as TPS finished 3rd in the 2009 Veikkausliiga.
On 16 July 2009 Andreasen signed a two-year contract with Danish 1st Division side Thisted FC.[4] Andreasen immediately became a regular starter for Thisted. He scored his first hat-trick in a professional game in a 4-4 draw against Kolding FC. He scored 7 goals in 15 games in the fall of 2009 but was then unfortunate to suffer an injury to his tendon. The injury saw Andreasen ruled out for nearly a year and he would not play until his comeback on 10 October 2010.
In January 2011 Andreasen had a setback, and had surgery for his tendon problem. He made a new comeback in May 2011.
On 1 June 2011 Andreasen went back to Randers FC, and played for the reserve team.[5] This was a part his recovery after the surgery.
In March 2012 Andreasen signed with the Norwegian team Flekkerøy IL,[6] after 27 goals in 39 games Andreasen went back to Denmark and signed the Danish 2nd Division side Skive IK in August 2013.[7]