The main Gallery building was originally designed by Melbourne architects Grainger & D'Ebro to house not only the art gallery but also the City Council offices, lecture theatre and public library. It is constructed of brick and plaster in an early French Renaissance style and was completed in 1887, with an extension built in 1916. It is three storeys high, with an attic in the steep pitched roofs, and a six storey clock tower. The building was registered as a Category I heritage item by the New Zealand Historic Places Trust on 24 November 1983.
The new building eventually proved too small to house all the Council departments and overflow space in the Customs House in Customs Street was found to be necessary. Following the completion of the Auckland Town Hall in 1911, all Council departments left the Gallery building allowing expansion of Gallery facilities, including extra workshop space for art classes.