Historical records from the 1650s paint a vivid picture of the site during its heyday; the Down Survey depicts the castle alongside four dwellings, whilst the Civil Survey provides more detail, describing ‘a castle lately repaired at ye States charge with a bawne, two thatcht houses within the same & 12 houses & cabbins abroad’. The property belonged to James Tobyn, recorded as an ‘Irish Papist’, until the Tobins forfeited it in 1653 following the tumultuous events of the 1641 Rising.

The castle’s strategic importance continued well beyond its medieval origins. Following the 1641 Rising, Killaghy became one of several garrison points established to suppress remaining resistance forces throughout the late 1650s. Later passing to the Despard family, the castle saw military action once more when it was garrisoned during the 1798 Rebellion. The Despards left their architectural mark on the property, adding an 18th-century castellated wing that extends westward from the original tower house, complete with decorative battlements that echo the defensive character of the earlier structure.

Today, the castle complex presents an intriguing mix of historical periods and modern adaptations. The two-storey, five-bay castellated wing adjoins the tower house, creating a small enclosed courtyard to the rear. A larger courtyard to the northwest is formed by converted outbuildings, now serving as holiday apartments, and enclosed by walls on the remaining sides. Whilst the original bawn mentioned in the 17th-century surveys remains unlocated, the layers of construction and adaptation at Killaghy tell a compelling story of continuity and change in the Irish landscape, from medieval stronghold to rebellion garrison to modern tourist accommodation.