In the later years of the fifteenth century, the MacLeods of Assynt decided to build themselves a castle on a good defensive site at the northeastern end of the loch. This first castle was a comparatively simple rectangular block of some three or four storeys.
About a century later Donald Ban, ninth MacLeod of Assynt added a tower with a stair and two upper rooms with fireplaces and also creating vaulted cellars and a vault over the great hall.
In 1650 the MacLeods imprisoned the Marquis of Montrose in the castle. At the time many Scots saw Montrose as a traitor, but within twenty years the political situation changed and it was the MacLeods who were being vilified. This played into the hands of the MacKenzies who achieved their long-nurtured ambition to acquire Assynt through a siege of the castle in 1672.