After Adolf Hitler and the NSDAP seized power in 1933, the National Socialists also misused Augustusburg Castle for their purposes. 
The complex was used as a training facility and a national training camp for spreading National Socialist ideology. In addition, the gatehouse served as prisons for political opponents of the regime.
To provide space, existing institutions – including the youth hostel and the regional exhibition – had their rental contracts terminated. renovations had to be carried out by prisoners from the nearby Sachsenburg concentration camp. Augustusburg Castle served as its subcamp. During the Second World War, refugees, a maternity ward and furniture evacuated from the Berlin Reich Chancellery were also housed in the castle.
Towards the end of the war in 1945 the National Socialists planned to detonate the castle – however, this order was never carried out.