Matthiesen was born in 1964 and grew up in Lower Saxony. He studied history, political science and geography in Göttingen and gained a doctorate in political science. He is a professional local journalist and has worked for the Waldeckische Landeszeitung (Korbach), the Flensburger Tageblatt and the Weser-Kurier (Bremen). He has been editor-in-chief of the General-Anzeiger Bonn since January 2015.