Today, the castle appears as little more than a pile of rubble, though it likely measured around 20 metres from east to west in its heyday. The site reveals grass-covered wall footings of a bawn wall to the south of the tower house, with a defensive ditch visible on the eastern and southern sides, creating an earthwork that resembles a ringwork encircling the stone castle.

The castle's history is well documented, with the O'Doyne Manuscript recording that Tadhg Mac Laighnigh Ui Duinn (O'Doyne) built this fortification in 1475. By 1608, the complex had grown considerably; records describe a castle with a hall, parlour at the hall's end, kitchen, brewhouse, and bakehouse, all contained within the bawn. The property also featured a haggart and additional bawns on the south side, plus gardens, an orchard, a park, stables, and cattle houses on the west side. The northern and western parts of Castlebrack town contained houses and tenements for tenants and various other purposes.

The castle saw further military significance during the Williamite Wars, when Colonel Terence O'Dunne repaired and strengthened it with extensive outworks in 1680. Intriguingly, the site may conceal even older secrets; in the early 18th century, a tenant farmer named L. McEvoy discovered subterranean passages beneath what O'Hanlon described as a 'remarkable moat at Castlebrack'. This moat, which enclosed the bawn, was possibly part of the 1680 defensive improvements, adding another layer to this site's complex military history.