The castle's rectangular tower house, built from limestone rubble, was originally protected by a fortified bawn wall, though today only a single circular tower survives from these outer defences. Standing 20 metres north of the main tower house, this round tower once formed the northwest corner of the bawn; a sketch from the 1890s shows that a connecting wall once ran between the circular tower's south face and the tower house's north face, creating an enclosed defensive courtyard.

The surviving circular tower offers fascinating insights into medieval Irish castle architecture. Rising four storeys with an internal diameter of roughly 2.9 metres and walls measuring 1.3 metres thick, it's built from roughly coursed limestone rubble. Entry is through a round-headed doorway on the southeast side, with a staircase leading up to the first floor; the upper levels would have been accessed by stairs across wooden floors that have long since rotted away. Each level served different purposes: the first floor features a west-facing window that was later converted into a fireplace using brick, whilst the second floor contains a garderobe and the third floor has another fireplace. The floors were supported by slight offsets in the walls, and remarkably, the parapet still crowns the tower with its distinctive long merlons and narrow crenellations.

The castle's history took a dramatic turn during the Cromwellian conquest of Ireland. In 1654, Richard Fitzgerald, the last Baron of Burnchurch, was forcibly transplanted to Connacht as part of Cromwell's policy of removing Catholic landowners from their estates. His ancestral possessions were then granted to Colonel William Warden, marking the end of centuries of Fitzgerald rule at Burnchurch. Today, the castle holds the designation of National Monument number 321, preserving this important piece of Kilkenny's medieval heritage for future generations to explore and understand.