The original Fitzgerald castle was probably a tower-house or fortified house and was described as a square building with battlements erected in the 16th century, with a pointed doorway and a window flanked by a stone head. The branch of the Fitzgerald family that owned Waterford Castle were the descendants of Patrick Fitzgerald, son of the de jure 6th Earl of Kildare.
The current castle is a Gothic-style house built in 1895 for Gerald Purcell-Fitzgerald (1865-1946) which incorporates the fabric of an earlier (pre-1845) house, and parts of the medieval (pre-1645) tower-house. The designs were prepared by Romayne Walker and supervised by Albert Murrary (1849 – 1924). The construction is in unrefined rubble stone with fine cut-stone quoins and window frames and topped with Irish-style battlements.