North of the church close is a gateway leading to Castle Westerholt. It is decorated with a shell-shaped gable with a lion on either side. The castle was built in 1740 by the Paderborn architect Franz Christoph Nagel as a residence for Abbess Clara Franziska von Westerholt. It is a two-storey plastered stone building on a high base with two wings to the rear. The south-facing entrance features a curved stairway leading to a central round-arched doorway, above which is a balcony and the coat of arms of the abbess.
After the dissolution of the convent in 1811, the Prussians took possession of the building. In 1841 the von Merveldt family bought it and, through marriage, it is now the home of the von Westerholt family.
To the side of the gateway are the eaves and wall of a two-storey half-timbered house with an overhanging upper floor. It was built as a gatehouse in the middle of the 16th century; the date on the brick gable refers to the restoration carried out by the Abbess von Korff.