The castle is within the registration county of Stirlingshire, although it is only 2 kilometres (1.2 mi) north of Milngavie, East Dunbartonshire, on the northern outskirts of Greater Glasgow.

[4] In 1682 the Grahams bought Buchanan Auld House near Drymen, a dwelling more fitting the title of "Marquess", though the family's official seat was kept at Mugdock Castle for a some time.

[2] He had the 17th-century mansion demolished, and commissioned a Scottish baronial style house to be built in the ruins of the old castle.

[2] In 2022 the dignity 'Baron of Mugdock' was transferred by assignation to Luciano Francesco Silighini Garagnani Lambertini, Lord of Ufford Hall.

It may have been shield-shaped on plan, comprising towers arranged around a courtyard, and linked by curtain walls and ranges of buildings.

The castle stood on a natural, steep-sided mound formed of hard volcanic rock, at the west edge of Mugdock Loch, which was larger than its present extent.

[10] Of the early castle, only the south-west tower remains complete, and forms the most recognisable feature of the ruins.

The narrow tower is of four storeys, with an entrance on the first floor, accessed via exterior steps on the east side.

On the outside, a line of corbels projects the two upper storeys out from the lower levels, giving the tower a distinctive "top-heavy" appearance.