The Windsor Castle is an early hotel in the inner Auckland suburb of Parnell. Once believed to be a late nineteenth-century structure, a detailed examination of the building in 1997 showed that much of it belonged to the 1850s and that it had subsequently been remodelled. Inns were important places of recreation and gathering in the earliest years of colonisation, and provided accommodation for a largely transient population. The discovery that the Windsor Castle dated from this period led to a reappraisal of its significance and helped to save the building from possible demolition.

The building is located on the site of an earlier inn, and was used as a pub and accommodation house for nearly 150 years. Originally a two-storeyed brick structure with a hipped roof and porch, the building lay on a major road leading south from colonial Auckland, in the nearby settlement at Parnell. Its symmetrical Georgian style and domestic character was typical of early colonial inns, providing small bar rooms on its ground floor and accommodation above. The hotel was remodelled in the 1880s, when the architect, R. MacKay Fripp, was commissioned to create a large Victorian corner pub of urban type. An elaborate Italianate facade was added, which still dominates its appearance. Surviving the general decline of the public house in the early twentieth century, the building has since been converted into a restaurant. This has substantially affected its ground floor area but left much of its upper levels intact.

The Windsor Castle is significant as one of the earliest surviving hotels in current-day Auckland and is among the oldest remaining brick buildings in the region. Its fabric is of value for demonstrating early pioneer construction techniques and materials, and the organisation of hotel accommodation. Its design demonstrates the importance of hotels in early colonial society, as well as their changing role and appearance in the later nineteenth century. The building has connections with the brewing trade, including companies such as Ehrenfried's and Speights, and was an important place of working-class recreation through much of the twentieth century. One of its architects, R. MacKay Fripp, made important contributions to the development of the Arts and Crafts movement in Canada, as well as the Californian bungalow in New Zealand and the USA. The building makes a strong contribution to the streetscape of Parnell, and adds considerably to the historic character of the suburb.