After gaining his doctorate degree in history and political science, Knopp worked as a newspaper editor at the Welt am Sonntag and the Frankfurter Allgemeine Zeitung. In 1978 he took up employment at the German TV station ZDF. Since then, he has produced many documentaries about the Nazi dictatorship like Hitlers Helfer ("Hitler's helpers"), Hitler-Eine Bilanz ("Hitler-taking stock") or Die SS: Eine Warnung der Geschichte ("The SS: A warning from history"), but also for example Vatikan (about the power of the popes) or Kanzler: Die Mächtigen der Republik (about Germany's post-war federal chancellors). He also hosts a weekly show on German television, usually broadcast on Sundays, called "History". In 1999 he produced a series called "100 Jahre - der Countdown", which sums up the whole 20th Century year by year and is still sometimes broadcast, mainly during holidays, by the German TV station Phoenix.

For the publication of his book "Top Spies - Traitors in the secret war" (1994) Knopp worked with the German Federal Intelligence Service and several retired spies to present their personal story and explain their work to a broad public.

Guido Knopp's history films are often attacked as presenting the Third Reich too superficially and as "editing history" so as to play down the role of the German public in building and supporting the Hitler regime.. Knopp has been criticized for rewriting history by leaving out the role of the Wehrmacht (German Army) in the cruelties of World War II. In 2004 a group of international historians warned that documentaries like the one's produced by Knopp could reduce important historic facts to mere infotainment. In 2003 Guido Knopp plead for Konrad Adenauer to be featured in the Unsere Besten list of greatest Germans, compiled by ZDF TV.

In 2004 he received the Goldene Kamera and the Bavarian and European TV award for his work.

Today he teaches Journalism at the Gustav-Siewerth-Akademie in Weilheim-Bierbronnen (Baden-Württemberg) and is living in Mainz. His publishing house is the German Random House group (Bertelsmann group).

In 2008 Knopp worked on a movie about the failed Hitler assassin Stauffenberg.

• Hitler's Holocaust. Sutton Publishing. ISBN 0-7509-2700-3
• (1998) Hitler's Henchmen. Sutton Publishing. ISBN 0-7509-3781-5
• (2002) Hitler's Hitmen. Sutton Publishing. ISBN 0-7509-2602-3
• (2003) Hitler's Women. Routledge. ISBN 0-415-94730-8
• Hitler's Children ISBN 0-7509-2732-1
• (2007) Die Wehrmacht: Eine Bilanz, C. Bertelsmann Verlag. ISBN 978-3-570-00975-8