The castle’s history stretches back to at least 1611, when Captain Roger Atkinson was granted ‘one ruinous castle’ along with various properties that had been confiscated from Levalian Nugent following his attainder. By 1641, the lands had returned to the Nugent family, with Andrew Nugent, described as an ‘Irish Papist’, recorded as the owner. The Down Survey maps of 1654-56 clearly depict a castle standing in this location, part of a network of fortifications that included nearby Culleenmore Castle, Castlemitchel, and Walshestown Castle.

Today, only fragmentary remains of the medieval structure survive; low wall footings running north-northwest to south-southeast, standing about a metre high and stretching just over seven metres, along with a three-metre-high fragment of the castle’s southeastern corner. A later buttress was built against the walls, though no cut stone fragments or architectural features definitively dating to the medieval period have been identified. The site’s most intriguing aspect may be Tullaghan House itself, built in 1779 as evidenced by a datestone bearing the initials ‘L.N.’ carved into the lintel above the doorway.

The National Inventory of Architectural Heritage suggests this Georgian house may incorporate fabric from the earlier castle or a subsequent structure that replaced it. The unusual arrangement of outbuildings at the front of the house, combined with a substantial chimneystack on the gable end and what was once an unusually long approach avenue from the southeast, all hint at an older building’s bones beneath the 18th-century exterior. Whether the house truly contains remnants of the medieval castle or simply occupies its footprint remains a tantalising question, adding another layer to this site’s centuries of Nugent family occupation.