Oamaru Police Station and the Lock Up, designed by Government Architect John Campbell, and opened in 1919. The buildings have historical, architectural and social significance, having been centre of policing in Oamaru over their working life, and stand as substantially intact examples early twentieth century police buildings, providing evidence on the experience of incarceration and the practice of policing.

Oamaru’s first police station and gaol, built in the late 1860s on Thames Street, were prominent features in this bustling colonial town, located alongside the courthouse. They formed a cluster of official buildings reminding the populace of the costs of leaving the straight and narrow. By the second decade of the twentieth century, Oamaru’s larrikin reputation had faded, and the justice facilities were under used. In 1913, the gaol was disestablished and the Resident Magistrate was removed, and Oamaru was brought under the Timaru magistrate's Court District, where it remains. The Public Works Department designed the new police station, and the Public Works Department District Engineer C.J. McKenzie advertised for tenders in September 1917. On 1 November, 1919, Senior Sergeant Stagpoole sent the following memo to his superiors. 'I respectfully report that we moved from the old Police Station to the new Station in in Severn Street, Oamaru, yesterday 31 October, 1919.'"

The Police Station is built of Oamaru stone with a Marseilles tile roof. It is a two-storey block, with a flared hipped roof and a central gable with a porch on the front. The treatment of the stone is the main decorative feature of the building, with the quarry-faced ashlar contrasting with the dressed quoins and window facings. The paired windows are multi-paned, double hung sashes. The porch is classically detailed with columns supporting a flat arch. The Oamaru Mail described the Police Station in 1998. The ground floor includes the reception area and many small rooms used for day to day police operations. Upstairs was originally sleeping and living accommodation for five constables, later converted to offices and a recreation area. The bathroom was originally a separate building outside the back door, later used the fingerprinting room. Also associated with the police station is the lock up at the rear of the section, with its high, barred windows and thick timber doors. Another stone building once housed the horses that must have been an essential means of transport in the early days. In 2004, a new building was added to the east of the existing police station.

Like the police station, the lock up is built of Oamaru stone, with similar detailing. It is a rectangular in plan, with a hipped corrugated iron roof, punctuated by ventilators. The stone is quarry-faced ashlar, with dressed quoins. The doors are heavy timber, with a barred fanlight above.

In 2015, the building remains part of the Oamaru Police Station, with the lock up at the rear of the section.