This rectangular tower house, measuring 8 metres east to west and 7.8 metres north to south, features an added garderobe tower projecting from its southern wall. Though most of the structure now reaches only to the second floor, the south wall and southeast corner survive to the third floor level, offering glimpses of its original height. The castle underwent extensive renovations in the 1850s, though time has since taken its toll; the external facing stones of the west wall have been robbed out, revealing the rubble core beneath and the outline of an internal vault.

The castle’s interior reveals a complex layout typical of late medieval Irish tower houses. Entry is through a rebuilt ground floor doorway in the east wall, leading to a passage that provides access to the ground floor chamber and a spiral staircase to upper levels. The second floor houses the main chamber, approximately 7 metres by 5.2 metres, featuring a wide segmental arched window embrasure complete with stone seats and a single cusped ogee headed light. From here, a pointed arch doorway in the southeast corner leads to a small lobby with stairs ascending to upper floors and access to the garderobe chambers, which retain their lintelled slit windows and, in one case, an upturned window sill covering the garderobe chute.

Beyond its architectural significance, Kilcolman Castle holds a unique place in literary history. Originally a castle of the Earl of Desmond, who acquired it from the Barrys in 1430, it was granted to the English poet Edmund Spenser in 1590. Spenser composed much of his epic poem ‘The Faerie Queene’ here before being ousted and the castle burned during the Nine Years’ War in 1598. By 1750, it was described as being ‘almost level with the ground’, though recent excavations by Dr Eric Klingelhofer have uncovered fascinating details including the remains of corner towers, evidence of an Elizabethan parlour attached to the southeast corner of the tower house, and a medieval hall along the southern bawn wall. These discoveries, along with surviving traces of the bawn wall that once enclosed an area roughly 50 metres by 35 metres, help paint a picture of what was once a substantial fortified residence.