Standing on a tree-clad hillside, Rusko Castle is an altered 15th century keep, to which has been added a long and lower 17th century wing, which was ruinous and has been demolished. The rectangular keep rises to three main storeys and a garret within a corbelled-out parapet. There is a gabled caphouse at one corner.
The entrance, through a lobby, leads to the turnpike stair and to the vaulted basement. The hall on the first floor is a large chamber with a fine moulded fireplace.
The property was held by the Cairns, but passed by marriage to the Gordons of Lochinvar early in the 16th century and they held it until the 20th century. The castle was inhabited until around 1930, but then it became roofless. It was restored in the 1970s and is occupied.