First marked as ‘in ruins’ on the 1839 Ordnance Survey map, the castle’s deterioration was already well advanced by the Victorian era, and by the time of the 1908 survey, little had changed. What remains tells the story of a tower house typical of late medieval Ireland, built from irregular granite boulders with walls that slope slightly inward, a defensive feature known as a batter that helped deflect projectiles and strengthen the structure against siege warfare.

The most intriguing architectural feature is the projecting tower at the northeast corner, which once housed an unusual hybrid staircase; partly spiral, partly straight, encased within walls measuring roughly 1.8 metres thick. This tower originally featured wide, segmental arched windows that would have flooded the interior with light, though these were later blocked up to create narrow defensive openings, suggesting the castle saw periods of conflict where defence took priority over comfort. The ground floor consisted of three vaulted chambers, one large and two small, their stone ceilings providing both structural strength and fire protection for the upper floors.

Archaeological surveys conducted in 1945 noted striking similarities between Ballinree and nearby Rathnageeragh Castle, particularly in the design of the embrasures and vaulting systems, suggesting they may have been built by the same masons or during the same period of construction. Today, visitors to the site will find little more than a pile of rubble where this once proud fortress stood, yet careful observation reveals traces of the original walls and the footprint of those vaulted chambers, offering tantalising glimpses into the defensive architecture that once dominated the Carlow landscape.