Built as a defensive tower house, this compact fortification measures just 5.7 metres across internally, with walls an impressive 3.45 metres thick at the base. The Civil Survey of 1654-6 recorded it as ‘a little castle wanting repair’, noting that James, Earl of Ormond, had been its proprietor in 1640. The original entrance, a pointed doorway with an external chamfer on the south face, is now blocked, though its defensive features remain visible; visitors would have passed through a lobby with a murder hole overhead, whilst guards could observe arrivals through an internal window facing the main doorway.

The interior reveals the castle’s medieval defensive architecture alongside later modifications. The ground floor chamber, roofed with a dome vault that springs 1.4 metres above the current floor level, was originally lit by narrow single-light windows set within deep embrasures; traces of wicker centring can still be seen under the embrasure arches. A spiral staircase curves around the northwest and northeast sections of the wall, though many of its doorways leading to upper floors and mural chambers are now blocked. The guardroom on the east side has been converted into a small wine cellar, whilst modern alterations include windows inserted at various levels and a late doorway cut through a deep window embrasure in the west wall.

Victorian additions have significantly altered the castle’s appearance, including a nineteenth-century battlemented tower built at the edge of the western parapet and extensions on the southwest side. Three corbels support machicolations over the north, east and west sections of the tower, with drainage spouts between them and at the base of the parapet. The parapet itself, standing two metres high with crenellations of 0.8 metres, appears to be a nineteenth-century rebuild that may incorporate original medieval elements beneath. Two chimneys punctuate the roofline; one on the southeast section supports three pots, whilst a smaller single-pot chimney sits on the northeast. Despite these later modifications and the insertion of modern windows at multiple floor levels, Farney Castle retains much of its medieval character, offering a glimpse into the defensive architecture that once dotted the Irish landscape.