Internally, the principal room was the council chamber which featured leaded windows depicting science, engineering, truth, justice, fortitude, and faith.

[1] A statue of the shipbuilder and shipowner, Peter Denny, sculpted by Sir Hamo Thornycroft, was erected in front of the building in 1902.

[5] A pointed arch from the Collegiate Church of St Mary, which had been founded by Isabella, Countess of Lennox in 1454 and demolished to make was for Dumbarton Central railway station in the mid-19th century, was placed just to the south of the three cannon.

[6] A war memorial, in the form of a Celtic cross designed by the sculptor John Gilfillan, which was intended to commemorate the lives of local service personnel who had died in the Second Boer War, was erected just to the south of the arch and unveiled by the Lord Lieutenant of Dunbartonshire, Sir James Colquhoun, 5th Baronet, on 9 October 1904.

An extensive programme of refurbishment works, which included roof repairs and restoration of the council chamber, was completed at a cost of £1.4 million in 2018.