The rectangular tower, measuring 13 metres north to south and 10.1 metres east to west, rises four storeys high and bears the scars of centuries of modification, including a later building attached to its eastern side. The castle’s history is marked by destruction and renewal; it was razed by Elizabethan forces in 1595, with the current structure likely dating from the subsequent rebuilding period, as evidenced by its fine punch-dressed stonework and the notable absence of the barrel vaulting typically found in earlier medieval towers.

The defensive features of Cloghan Castle reveal the turbulent times in which it was built. The original bawn wall, though altered over the centuries with the addition of an 18th-century square flanking tower and outhouses at the southwest angle, still retains three of its original flanking towers and the wall walk. Two bartizans project from the main tower; one at the northeast corner at wall-walk level and another on the southwest angle at third-floor level, providing additional defensive positions. The original entrance on the east wall was particularly well-fortified, protected by both a machicolation and murder hole above the passage, with a spiral staircase in the southeast corner leading to the upper floors and a guardroom positioned in the northeast angle.

Inside, the tower reveals a sophisticated layout typical of its period. The ground floor featured wooden flooring supported on stone corbels, whilst the upper levels contain a series of vaulted chambers running north to south, accessed via the spiral stairs through elegant two-centred pointed doorways with chamfered, finely punch-dressed jambs. Comfort wasn’t entirely sacrificed for defence; large fireplaces warm the main chambers, with one on the west wall at third-floor level and another at ground level on the north wall. A mural passage in the south wall of the first floor leads to a garderobe in the southwest corner, whilst twin-light round-headed windows at third-floor level on the west wall, appearing to be original features, would have provided both light and views across the Shannon valley.