The Colonial Bank of New Zealand was a Dunedin institution formed to compete with the Bank of Otago. It spread throughout New Zealand. The Colonial Bank of New Zealand opened its first premises on Tyne Street in 1876. It quickly outgrew its temporary premises and arranged to lease Harbour Board land on the corner of Thames and Itchen Streets. The building has architectural, historical and social significance for its role as a provincial financial institution and for its strong visual contribution to the character of the centre of Oamaru.

The Oamaru Mail provides a detailed description of the new buildings. Thomas Forrester designed the new ‘temple of mammon’ which presented ‘a very pleasing appearance’, though marred by its ‘isolated situation’ marooned on the corner between Itchen Street and Oamaru Creek. The 44 foot high building had a 46 foot frontage to Thames Street and a 50 foot front to Itchen Street. Though not elaborate, it presented a ‘solid and substantial appearance, indicative, no doubt, of the nature of the business to be transacted within its portals.’ The main entrance from Thames street led to the banking hall (30 feet by 23 feet [9.1 by 7 metres], with a ceiling height of 19 feet [5.8 metres]) with its ‘massive cornice and centre ornament of 5ft. in diameter.’ The fittings were cedar. Other rooms included the manager’s room, next to it the strong room (14 feet by 20 feet [4.3 by 6.1 metres]). Behind the strong room were the caretaker’s apartments, consisting of a bedroom and sitting room. Upstairs were five offices, to be let separately. Some 18,000 cubic feet of Oamaru stone were used in its construction. The article indicated that the bank building should be completed in January 1878. Wilson, Roxburgh and Co. were the stone masons, while West and Sinclair completed the carpentry work.

The Colonial Bank is a ‘rather plain interpretation of the palazzo style.’ Art historian Conal McCarthy describes the building: ‘The ground floor is rusticated, with an order of very severe, paired Doric pilasters flanking round-headed windows, while the top floor has an order of Ionic pilasters. The façade is capped by a plain parapet.’ A small Doric portico emphasises the main entrance.

Offices were built to the east of the Colonial Bank for the South British Insurance Company in 1881. The North Otago Times reported that the new buildings ‘while improving the appearance of the bank premises will also fill up an unsightly gap in the main thoroughfare.’

In 1895, the Bank of New Zealand purchased the Colonial Bank. The Bank of New Zealand occupied this building until 1969. After the bank vacated the building, the Oamaru Operative Society moved in.

In 2015, the former Colonial Bank is home to Oamaru’s I-Site information centre.