William Berry was born in Edinburgh, Scotland, probably in 1834 or 1835, the son of Margaret Garden and her husband, William Berry, a dyer. Around the age of 12 he was apprenticed in the composing room of the Scotsman newspaper in Edinburgh. He gained valuable experience in many aspects of journalism while occupying positions such as reader and assistant foreman in the office. Berry's contact with the leading literary figures associated with the newspaper stimulated his efforts at self-education, and he was never to lose the wide culture gained in these years. On 5 July 1860 he married Henrietta Younger at Edinburgh; they were to have three daughters and three sons.
In 1863 Berry was engaged by the Daily Southern Cross newspaper in Auckland, New Zealand, as a war correspondent. With his wife and two sons he arrived in the Royal Stuart at Auckland on 26 January 1864. In the course of his duties he made the acquaintance of C. O. B. Davis, who may have helped him acquire his knowledge of the Māori language. He later became a sub-editor on the Southern Cross. In 1868, in order to arouse public indignation, he apparently wrote a letter to the paper pretending to justify the shooting of Hauhau women and children by Māori acting under military orders; it was signed 'Exterminate'. The paper was soon faced with a loss of advertising revenue and Berry was forced to resign.
From 1868 Berry was editor of the Thames Advertiser. The paper was purchased in 1874 by William Wilkinson and Alfred Horton, owner of the Southern Cross. Berry moved to Auckland in 1875 as editor of the New Zealand Herald, and retained this position when it merged with the Southern Cross in 1877. Between 1875 and 1903 Berry took the Herald to a leading place among the newspapers of the colony. Although his term also coincided with a general advance in news presentation methods, he achieved a liveliness in the leading articles, a widening of the paper's cultural interests – especially in music and literature – and a distinct moderation in its earlier hostility towards Māori. He had acquired a sound knowledge of Māori history, and showed a sympathy with Māori and an understanding of issues affecting them.
Under Berry's editorship the Herald opposed the abolition of the provinces in 1876 as this would still leave Auckland economically disadvantaged and without the benefit of a local legislature. In 1879 the paper supported Sir George Grey as the champion of northern development. It supported the attack on Te Whiti's village at Parihaka in 1881, because it would lead to the opening up of a fertile area of the country for European settlement.
Berry was widely respected as a journalist and editor. He had an extensive knowledge of local and national politics, and his occasionally waspish sense of humour found an outlet in the weekly 'Local gossip' column. It was Berry who instigated George Reed's April Fools' Day joke, printed in the Herald, about the discovery of Noah's Ark on Mt Ararat.
Berry was completely devoted to his work and apparently had little time for other interests. He was, however, asked to help in selecting the first 3,000 volumes for the Auckland Free Public Library in 1880; he was a member of the library's advisory committee until his death. In 1902 or 1903 he was elected president of the New Zealand Institute of Journalists.
William Berry died suddenly at his residence, Te Muritai, at Lake Takapuna (Lake Pupuke) on 2 October 1903. He was buried at O'Neills Point cemetery, Takapuna. Henrietta Berry died on 9 January 1918.