Hermann Giesler completed his architectural study at the Academy for Applied Arts in Munich.
Up to 1938 he designed the "Ordensburg" in Sonthofen; planned Gau Forums in Weimar and Augsburg; and the "university" for the NSDAP at Chiemsee.
Starting in 1941, after fellow architect Roderich Fick fell out of political favour, Giesler was entrusted by Hitler with the reorganization of the entire city of Linz.
Giesler joined the Nazi Party in 1941 in Organisation Todt (OT) as head of the "Assembly for the Baltic States Giesler", as head of the Einsatzgruppe Russia North of the OT (1942–1944), and as Director of the OT-Einsatzgruppe VI (Bayern und Danube gaue).
In 1947, he was indicted by a U.S. military court for war crimes in the concentration camp Mühldorf, a subcamp of Dachau.