The rectangular tower house, measuring roughly 8.6 metres by 7 metres, dates back to at least 1634 when John Cullen held both the castle and 80 acres of surrounding land. The Cullen family’s prominence in the area stretched back to the mid-16th century, with John Collin serving as a Member of Parliament for Clonmines in 1637. By 1640, Thomas Cullen had expanded the family holdings to include 180 acres at Cullenstown and an additional 100 acres at nearby Cullensland, though his fortunes would shift dramatically under Cromwellian rule when he was assigned 732 acres in distant Connaught as part of the forced resettlement policies of the 1650s.

The tower itself reveals the defensive priorities of its builders through its surviving architectural features. Visitors entering through the original lintelled doorway on the northwest wall would have passed beneath a murder hole; a sobering reminder that hospitality wasn’t always guaranteed. A mural staircase winds upward through the structure, connecting the ground floor with its four embrasures to the first floor, which sits beneath a barrel vault running northeast to southwest. The second floor chamber, accessed through a narrow passage in the northeast wall, still retains traces of its domestic comforts including window seats and a granite fireplace mantel supported on corbels, suggesting this was likely the principal living space for the castle’s inhabitants.

Though adapted as a modern dwelling with a two-storey extension added around 1790-1800, and crowned somewhat incongruously with concrete crenellations, the castle maintains its defensive character within what appears to be the remains of a bawn. This outer enclosure, defined by an earthen bank and hedge along its southwest and northwest sides, once measured approximately 64 metres by 40 metres, creating a protected courtyard typical of Irish tower house complexes. Located just 200 metres from a medieval church site, Cullenstown Castle formed part of a broader settlement pattern that characterised this corner of County Wexford, where Anglo-Norman and Gaelic Irish traditions merged and clashed across the centuries.