The structure, measuring approximately 8.45 metres north to south and 12.65 metres east to west, was likely no taller than two storeys; a relatively compact fortification by medieval Irish standards. Built with rubble limestone, the tower's thick walls, measuring 1.25 metres across, would have provided both security and insulation for its inhabitants.

Time hasn't been particularly kind to Black Castle, with the northern and eastern walls having collapsed entirely, leaving only the southern and western walls to tell the structure's story. These surviving walls display a slight base batter, a common architectural feature where walls slope outward at the bottom for added stability. The remaining architecture is refreshingly unadorned, featuring only the most practical elements: simple cubby holes for storage, plain splayed window openings that would have allowed defenders to shoot arrows whilst minimising their exposure, and an intramural staircase cleverly built within the western wall's thickness to provide access to the first floor.

Archaeological surveys have noted possible earthworks on the northeast side of the castle, suggesting that the tower house may have been part of a larger defensive complex or had associated outbuildings that have since disappeared. These subtle ground features hint at a more extensive medieval settlement, though without excavation, the full extent of Black Castle's original footprint remains a matter of speculation. The castle stands as a testament to the proliferation of tower houses across Ireland during the late medieval period, when local lords required fortified homes to protect their families and assert their territorial claims.