This tower house has a storied past, documented as early as 1504 when Mac William De Burgo launched a destructive campaign against the O'Kelly family's strongholds, targeting their castles at Monivea, Gallagh, and here at Garbally. What remains today is the northeastern half of what was once a rectangular three-storey tower, measuring over 8.3 metres in length and 9 metres in width.

Despite centuries of weathering, the surviving structure offers fascinating insights into medieval defensive architecture. The original entrance, located at the eastern end of the southeast wall, features a pointed arch doorway with a gun loop built into its southern jamb; a clear indication of the castle's military purpose. This doorway is particularly intriguing, framed by an outer arch with a narrow slit between it and the door proper, creating an effect similar to a murder-hole. Once inside, visitors would have found themselves in a small lobby with an actual murder-hole overhead, whilst an intramural staircase, now broken, led up from the lobby's south side to the first floor.

The castle's defensive features extend throughout its construction. A stone vault once separated the first and second floors, though both levels are now inaccessible. The northwest wall contains a mural passage on the first floor and a chamber on the second, whilst corbels that once supported machicolations; defensive structures that allowed defenders to drop objects on attackers below; can still be seen atop the northeast and southeast walls. The windows range from simple defensive slits to more elaborate single and two-light openings with distinctive ogee heads, typical of late medieval Irish architecture. Rather unusually, a handball alley now abuts the outer face of the northeast wall, a modern addition to this ancient fortification.