The Supreme Court (now High Court) Building is a powerful example of Gothic Revival architecture, and was one of the most impressive buildings in New Zealand when built. It was constructed in 1865-1868 under the direction of Edward Rumsey, a British-born architect who had trained under Gilbert Scott. The two-storey brick and stone building replaced an earlier courthouse in the commercial sector of colonial Auckland, which had been built of kauri timber. The new structure was erected in a more elevated and prominent position, prestigiously located alongside the now-demolished Provincial Council building and the former Government House. This occurred at a time of uncertainty about Auckland's future, soon after the colonial capital had been moved to Wellington and while the British Army troops at nearby Albert Barracks were being withdrawn.

The courthouse was one of the earliest large-scale construction projects in the town, being proclaimed at the time to be the first public building of durable materials erected in Auckland Province. A distinctive Gothic Revival style was employed for its exterior, including a crenellated central tower and pointed-arch arcading. This style was extended to its internal features, contrasting strongly with the classical appearance of earlier structures nearby, including St Andrews Church and the former Government House. Gothic Revival was frequently used in larger judicial buildings during the later colonial period alluding, in part, to the longevity and power of the British justice system through the use of medieval imagery. Extensive carvings by Anton Teutenberg on the main facades of the Auckland courthouse reinforce such notions of authority, with naturalistic depictions of British royalty, local dignitaries and Maori leaders, such as the Ngapuhi chief, Hone Heke (d.1850). The building was extended in 1935-1936, and more extensively in 1988 when part of the original structure was removed to accommodate new facilities. The interior retains its main original courtroom, including its timber panelling and gallery. The courtroom also contains other items of historic value, such as graffiti on the journalists' benches and a trapdoor in the dock for the accused.

The High Court is nationally significant as an early public building of Gothic Revival style, unusual in its scale and level of decoration in 1860s New Zealand. It graphically demonstrates the growing power of the state and legal system on a national level, as well as the local importance placed on law and order as Auckland was undergoing transformation soon after the third New Zealand - or Waikato - War (1863-1864). The building is notable for its almost continuous use as a courthouse and has been closely linked to legal cases of national and international importance. These have included the earliest trial in New Zealand to involve fingerprint evidence, and the trial of those accused of sinking the 'Rainbow Warrior' in 1985. The building reveals much about nineteenth-century life through its appearance and layout, including attitudes to justice, the organisation of legal affairs and relationships between the public and the state. The preserved interiors also demonstrate prevailing fashions for decor and nineteenth-century craft techniques. The Teutenberg carvings have high aesthetic appeal, and form a significant group of early colonial sculptures. The significance of the building is enhanced by its imposing landmark qualities, and by being one of several structures on their original sites in the Waterloo Quadrant and Symonds Street area.