Finland became part of Russia after the war of 1809 ->. Ten years later, four rooms on the first floor of the castle were used as a prison.

The castle was renovated into a prison in 1836-1837 according to the plans of architect C. L. Engel. Over the years, the castle was completely adapted to the needs of the prison. Staircases and passageways were built in the medieval courtyard, which greatly altered the courtyard, to make it easier to walk around. On the third floor of the castle, small 1,3x2,4 m cells were built where the prisoners spent their nights. During the day, the prisoners worked in areas such as the prison weaving mill or the garden.

The women's prison in Häme Castle began in 1881. The women's prison ended in the main castle in 1953, but continued in the perimeter wall buildings until 1972. The most famous female prisoners at Häme Castle are Hertta Kuusinen and Elvi Sinervo, who were imprisoned for political reasons.