After the loss of their ancestral home, Spiegelberg Castle, the Counts of Spiegelberg acquired land in Coppenbrügge in 1281 from the canon monastery in Wunstorf. Together with other land acquisitions from Loccum Abbey, these formed the core of the new territory of the County of Spiegelberg around the town and the newly built moated castle of Coppenbrügge. The castle was also used to control the old military and trade route from Aachen to Königsberg, which led through a swamp area near the castle over a log dam. The castle was first mentioned in a document in 1303. The castle gate with its two flanking round towers, the foundations of the so-called brewery in the west of the castle courtyard and the surrounding moat probably date from this period. After the castle had been severely damaged during the "Spiegelberg feud" in 1434 - the counts were branded as robber barons - the Spiegelbergs, who had become impoverished in the meantime, inherited the county of Pyrmont in 1494 and rebuilt the castle in the style of the early Renaissance. Pyrmont Castle became the new seat of the Counts of Spiegelberg, and one administrator remained at Coppenbrügge Castle. In 1512 the castle was transformed into a fortress by building a rampart.
Merian engraving from Coppenbrügge Castle around 1650
After the death of the last Count of Spiegelberg in 1557, the castle passed to his brother-in-law Hermann Simon zur Lippe, the husband of Ursula von Spiegelberg and younger brother of Bernhard VIII zur Lippe. After the death of Hermann Simon's son Philipp, the castle passed to the Count of Gleichen-Thonna in 1585. From 1633 the castle was owned by Nassau and was already dilapidated in 1697. At that time it was the meeting point of Tsar Peter the Great on his journey with the "Great Embassy" from Moscow to Amsterdam with the Electress Sophie of Hanover and her daughter Sophie Charlotte of Hanover.
Before 1745 the House of Nassau-Oranien erected the new baroque palace on the north wall. The half-timbered building on the south side of the courtyard, which used to house the court, was probably built around 1800. After it was sold to the Kingdom of Hanover in 1822, the castle was demolished, and around 1870 the farm buildings followed, with the exception of a half-timbered house (office building) at the back of the courtyard. In 1945 the ruins were briefly used as a quarry. After that, the former office building was the seat of the Coppenbrügg district court and is now used as a museum.