The building of the castle began at the end of the 15th century. It is in the Gothic architecture style. Building of the castle was completed by Duke Ilinich in the early 16th century. Around 1568 the Mir Castle was owned by Mikołaj Krzysztof "the Orphan" Radziwiłł. He finished building the castle in the Renaissance style. A three-storey palace was built along the eastern and northern walls of the castle. 