After success in Bulgaria, he moved to Germany to play for Arminia Bielefeld but failed to establish himself within the first team. Trajanov made his début for Arminia in a 4–2 win over 1. FC Köln II in the DFB-Pokal on 21 September 2004, coming on as a substitute. He made his Bundesliga début on 12 December 2004 as a second-half substitute in a 5–0 defeat to VfL Wolfsburg at Volkswagen Arena. This was to be his last appearance for Arminia.