Built or extensively remodelled in the early 17th century by Sir Geoffrey Galwey, a prominent lawyer who served as mayor in 1600, the structure incorporated elements from an even older building that local tradition claimed was part of the medieval palace of the kings of Limerick. The Galwey family, originally a branch of the Burkes, had deep roots in the city; their ancestor John de Burgo was knighted in 1361 for defending Balls Bridge against the O'Briens, and a fine family monument from 1414 still stands in the cathedral.

The castle's architecture told the story of Limerick's turbulent past and changing fortunes. Its original Elizabethan features included pointed gables and stone mullioned windows, with a round arched doorway opening onto Gridiron Lane, named after a popular inn run by one Pat McGrath, nicknamed "Paddy the Chopper". The building's most distinctive feature, however, was its high Dutch gable front of red brick facing Nicholas Street, reportedly the first brick fronted house in Limerick. This Dutch style addition likely dated from after 1661, when Lord Orrery actively encouraged Dutch merchants to settle in the city following the Cromwellian conquest. The castle had gained notoriety as "Ireton's House" after Sir Geoffrey Galwey's grandson was hanged by Cromwell's son in law Henry Ireton in 1651 and the property confiscated, though records show £20 was spent on preserving the building between 1650 and 1654.

Despite being one of the few castellated houses to survive the devastating 1691 siege of Limerick, Galwey's Castle met its end not through war but through Victorian sensibilities. When the Dean and Chapter purchased the property in 1894 with plans to close Gridiron Lane, the Corporation refused to preserve it, apparently due to lingering prejudice against its association with Ireton. The demolition of this large stone structure, which had stood as a tangible link to Limerick's medieval and early modern past, was lamented by antiquarians of the time who recognised it as one of the most remarkable examples of the city's old castellated houses. Its loss meant the disappearance of a building that had witnessed the rise and fall of Gaelic nobility, English conquest, Dutch trade, and centuries of urban life in one of Ireland's most historic cities.