Henry Brett was born at St Mary Magdalen, near Hastings in Sussex, England, on 25 February 1843, the son of Henry Brett, a tailor, and his wife, Mary Ann Elizabeth Hallows. Henry was initiated into publishing in his home town by his uncle, T. R. Brett, a newspaper proprietor and stationer, and local historian. In 1862 he emigrated to New Zealand aboard the Hanover, with the idea of combining newspaper work with development of 40 acres of land he had bought in the Albertland settlement on the Kaipara Harbour. The farming proposal was stillborn. When the Hanover dropped anchor in Auckland harbour on 17 September the proprietor of the Daily Southern Cross boarded the ship looking for reporters, and hired Brett as a marine reporter. Newspapers became Henry Brett's life from then on.
Brett won recognition as an outstanding reporter while working on the Daily Southern Cross for three years and then for five years on the New Zealand Herald. He lived at Parnell in sight of the Mt Victoria signal station. Day or night, once a ship was signalled as being in the Rangitoto channel, he would rush to the waterfront and hire a waterman to row him out to the ship to get the latest overseas news.
In 1870 Brett left the Herald and bought into the Evening Star (later the Auckland Star ), beginning more than 50 years as a newspaper proprietor. He introduced innovative ideas to increase circulation, including the purchase of a flock of pigeons to carry news from the Thames goldfields and elsewhere. In 1876 he became the sole owner of the paper, appointing his sub-editor, T. W. Leys, as editor. Under their partnership the Star flourished. By 1898 it claimed to be the most widely circulated paper in New Zealand with a daily sale of over 15,000. Leys had become a partner in the business in 1889 and in 1900 Brett and Leys formed the Brett Printing and Publishing Company.
Brett introduced photo-engraving in New Zealand, bringing out the illustrated weekly New Zealand Graphic in 1890. In addition to newspaper publishing he produced a number of popular guidebooks and almanacs, including Brett's Auckland Almanac, Brett's colonists' guide, Brett's gardening guide and Brett's New Zealand and South Pacific pilot. He was also an important publisher of historical works, the most significant being R. A. Sherrin and J. H. Wallace's Early history of New Zealand (1890). He combined his interests in history and things maritime when he wrote and published White wings (1924–28), a two-volume history of the ships which visited New Zealand between 1850 and 1900 (the second volume published posthumously). With Henry Hook he wrote a history of the Albertland settlement, The Albertlanders (1927).
The Star had backed George Grey in the parliamentary election of 1875, and was a supporter of the Liberal administrations of John Ballance and Richard Seddon, but neither Brett nor Leys had strong political ambitions. Each declined the offer of a seat in the Legislative Council. However, Brett played a part in local politics, as chairman of the Parnell Highway Board, a member of the Auckland Harbour Board and the Auckland City Council, and mayor of Auckland for a year (1877–78). In 1878 he was appointed a justice of the peace and a member of the Auckland College and Grammar School board of governors, and he was at some time president of the Auckland Mechanics' Institute. He was also a founding member of the Newspaper Proprietors' Association of New Zealand and for some 40 years a director of the United Press Association.
Henry Brett had married a childhood friend, Mary Moon, at Auckland on 22 November 1864. From their first home in Parnell they had shifted to Takapuna in 1886. Te Kiteroa, on the southern shores of Lake Takapuna (Lake Pupuke), became one of the show-places of Auckland, and their hospitality renowned. One of the biggest gatherings in the spacious gardens was a picnic for the visiting Australian cricket team in 1896. More than 1,000 people attended, conveyed to Takapuna beach by chartered ferries which ran continuously from noon until 11 p.m.
The splendid grounds of Te Kiteroa reflected Brett's expertise in horticulture. Gardening was one of his two great interests apart from publishing. The other was music. His love of choral music led him to donate a magnificent pipe organ to the Auckland Town Hall when it opened in 1911, and he sang in choirs around Auckland for more than 50 years.
Henry Brett was knighted for his services to the public and the newspaper industry in 1926 after twice declining the honour. He died the following year while on holiday in Rotorua, on 29 January 1927. He was survived by his wife and four of their six children. After his death Mary Brett donated their Takapuna home to the Anglican church to be used as an orphanage. The Brett Printing and Publishing Company, since 1920 a public company, bought out the Lyttelton Times Company to form New Zealand Newspapers in 1929.