In 1181 the castle and town of Blankenburg were besieged, under the direction of Bishop Dietrich of Halberstadt, by imperial armies.

In 1386, according to legend, the Blankenburg was supposed to have been secretly looted in the night by Dietrich of Wernigerode, while Count Busso was absent.

In 1705 the conversion of the Renaissance castle into a Baroque residence was started by state architect, Hermann Korb, on behalf of Duke Louis Rudolf of Brunswick-Wolfenbüttel.

The family of the Duke Ernest Augustus of Brunswick (1887–1953) and his wife Duchess Victoria Louise, Princess of Prussia (1892–1980), lived in the castle from 1930 until their flight and the expropriation of their property in 1945.

In 1937, the Duke and Duchess hosted a ball here celebrating the engagement of their daughter Frederica with then crown prince Paul of Greece.

A few days before Blankenburg was handed over to the Red Army by British and US forces in late 1945, to become part of East Germany, the family was able to quickly move to Marienburg Castle (Hanover) with all their furniture, transported by British army trucks, on the presumed order of King George VI.

[1] Under the East German rule, the Technical College for Domestic Commerce was housed in Blankenburg Castle.

Following the closure of the school with the demise of East Germany in 1990 a long period began in which the castle was not used and the building became neglected as a result.

Years of decline followed, resulting in leaking roofs, permanent damp in the building and its infestation by dry rot, leading to a danger of collapse.