The barons of Sumiswald sold the castle and surrounding lands to the city of Bern.

Trachselwald Castle became a prison where Mennonites were held, some of whom were then executed for their beliefs which differed from the ruling Reformed Protestants.

In 2021 an exhibit opened in the castle's prison documenting the oppression of Mennonites in the region.

The keep and outer walls are made of tuff stone cut into roughly squared blocks which indicates construction before 1200.

[5] The new additions were built in a Romanesque style, which included larger windows and thinner walls.