In June 2008, Mitsanski transferred to Zagłębie Lubin. In the 2008–09 season, he became the top goalscorer for the team in the Polish First League with 26 goals, helping his team win promotion. During the next season Mitsanski finished second goalscorer in the Polish league with 15 goals, just 2 goals behind the Polish rising star Robert Lewandowski.
On 18 June 2010, Mitsanski signed a four-year contract with 1. FC Kaiserslautern. On 24 July, he netted the only goal in the prestigious 1–0 win against Liverpool in a friendly match. On 22 September 2010, he made his official debut for his new team in the 0–5 away loss against Borussia Dortmund after coming on as a substitute for Erwin Hoffer. On 13 November 2010, Mitsanski scored his first goal in the Bundesliga in the 3–3 home draw with VfB Stuttgart. He was unable to establish himself as a regular for the team and was loaned out to FSV Frankfurt during the winter break.
On 11 August 2010, Mitsanski made his debut for the Bulgarian national team in the 0–1 away loss against Russia in a friendly match. On 26 May 2012, Mitsanski scored his first goal for the team against the Netherlands, which was a dramatic last-minute win. Mitsanski scored his second international goal against Cyprus after coming off the substitutes bench in a friendly played on the 15th of August 2012.