Demtrøder has been active in German television, notably as a regular on Der Landarzt (The Country Doctor) as Wanja Teschner from 1992 until 2013, and a similarly long stint on the police series Großstadtrevier (1992-2010) as plainclothesman Henning Schulze. He was a regular on the soap opera Verbotene Liebe (2011-2014) and appeared in episodes of Leonie Löwenherz and Tatort.