The castle’s recorded history begins in 1546 when John Isham acquired it along with 120 acres from Robert and John Roche, though his ownership proved brief; following his death in 1553-4, the property returned to the Roche family through his eldest daughter’s marriage to a Roche of Bryanstown in 1558. By 1641, according to the Civil Survey, Nicholas Roche held a castle described as being in “indifferent repair” along with 200 acres, suggesting the fortification had already seen better days by the mid-17th century.

The Cromwellian period brought significant change when the estate passed to the Tench family, later transferring through marriage to the Leslies in the 18th century. Between 1879 and 1850, a branch of the Sweetman family called Bryanstown home, adding another layer to its complex ownership history. Today, what remains of the original tower house has been ingeniously incorporated into the modern Bryanstown House, preserving its medieval bones whilst adapting to contemporary needs.

The architectural features of the surviving tower reveal its defensive origins; positioned on a gentle east-facing slope, the structure retains a north-south barrel vault over the first floor, with the original first and second upper storeys now functioning as a single space. Evidence of its fortified past persists in the blocked window lights set within embrasures in the west wall at ground level, whilst a projecting tower at the northeast corner once housed a staircase, now blocked, that provided access to the first floor through a doorway that has also been sealed. These modifications chart the building’s evolution from medieval stronghold to country residence, a transformation common to many Irish tower houses that survived into the modern era.