The castle was transferred through marriage to Count Gerhard I of Jülich-Berg, who had been married to Bernard's niece Margaret since 1338, and its function as the ruling seat was lost.

Around 1530, a round bastion was added in the west, only accessible from the castle itself via a bridge, from which one could control Bielefeld Pass with artillery.

The description Scherpentiner can only be verified at the Sparrenburg, its origin can be traced back to the Serpentinen (Serpentin = Italian for snake; German Feldschlange, culverin), which are light artillery guns of the 15th and 16th century.

The collective government, arranged in 1609 by the main heirs John Sigismund, Elector of Brandenburg and duke Wolfgang Wilhelm, Count Palatine of Neuburg failed and culminated in the War of the Jülich Succession.

Due to the Treaty of Xanten, signed in 1614, which ended the succession conflict, the castle was handed over to Brandenburg-Prussia, which immediately granted the right of occupation to its Dutch confederates.

[2] In 1623, in the course of the Thirty Years' War, which broke out in 1618, the Dutch had to retreat before the overpowering advance of the Spanish, led by count John III von Rietberg.

The outer walls were torn down by agreement of King Frederick II of Prussia and were used for the construction of the barracks 55, which still stands at the Hans-Sachs-Straße.

Used as a flak emplacement during World War II, the Sparrenburg was heavily damaged in the course of the air raid on Bielefeld on 30 September 1944; only the tower remained undamaged.

[3] A new visitor centre designed by Max Dudler[4][5] on the southeast edge of castle's courtyard was opened in September 2014.

Inside the 80 square metres (860 sq ft) single-storey building with compressed concrete walls are integrated museum gift shop, ticket counter and kiosk.

An attraction is the annual Sparrenburgfest held on the last weekend of July, where carnies and merchants re-enact the medieval way of life.

In view of the estimated restoration costs of 7.5 million euro Bielefeld's Townsmen Foundation continues to seek further donations even after the end of the adoptions.