In early 1869 at the age of 25 he moved to Dunedin in New Zealand where a volume containing a selection of poems he had written in Australia was published. While working as a shearer and at various odd jobs, he carried on writing, and published a small book of verses Flights among the Flax. This was noticed in literary circles, and he won the Otago Caledonian Society’s prize for poetry.

Determined to enter journalism, Bracken took a staff position on the Otago Guardian (and also wrote for The New Zealand Tablet and the Morning Herald). While at the Guardian he met John Bathgate who soon after, in 1875, established the Saturday Advertiser  'to foster a national spirit in New Zealand and encourage colonial literature'.

Bracken became editor and immediately began to encourage local writers. Talented contributors were attracted and the Advertiser’s circulation reached 7000 copies which was a notable achievement for that era. Encouraged by this literary and commercial success, Bracken contributed some of his own satire, humour and verse, including God Defend New Zealand published in 1876 which was widely admired and became the national anthem. He wrote Not Understood in 1879.

Although he often used the pseudonyms Paddy Murphy and Didymus, the prolific works under his own name soon became published worldwide and he became famous throughout Australia and New Zealand. Later publications of his works in bound editions included Flowers of the Freeland, Behind the Tomb and Other Poems, The Land of the Maori and the Moa, Musings in Maoriland and Lays and Lyrics: God’s Own Country and Other Poems.

A supporter of the egalitarian policies of Governor Sir George Grey, Bracken championed sovereignty for the native Māori people, and later criticised the government for what he saw to be breaches of its obligations to the Treaty of Waitangi.

He had arrived in New Zealand when colonial troops were engaged in war with Chief Te Kooti who went into battle under his own distinctive flag. It had three symbols which some claim were meant to signify stars. Bracken’s national anthem asks God to "guard Pacific’s triple star" and some historians have reasoned that refers to Te Kooti's flag and is his oblique support for Māori. It has also been suggested that"Pacific’s triple star" simply means the three main islands of New Zealand -- Northern, Middle and Stewart as they were referred to at that time. Bracken never explained what he meant, so there is no definitive clarification today. (There have been suggestions that Bracken was referring to Alpha Centauri, the very bright triple star in the Milky Way, visible only in the Southern Hemisphere. That is impossible because Proxima Centauri, the third star in Alpha Centauri, was not discovered until 1915, some 49 years after Bracken wrote his anthem.) Bracken was a freemason.

Vitally interested in current events and politics, Bracken stood for Parliament in the City of Dunedin electorate in the 1879 general election. He was unsuccessful at that time. However, Bracken won the Dunedin Central electorate at the 1881 general election. He lost the seat to James Bradshaw at the next general election but when Bradshaw died in 1886, he won the 1886 by-election and resumed his seat until the end of the term in 1887, when he retired.

He later established Thomas Bracken and Co with Alexander Bathgate to buy and operate the Evening Herald until it was superseded in 1890 by the liberal Globe.

Like many multi-talented and successful writers, Bracken was not a prudent person and eventually became financially embarrassed. He became a bill reader in parliament, but was forced to leave Wellington and return to Dunedin when his health deteriorated.

He died 16 February 1898, and is buried in the Dunedin Northern Cemetery. A lookout nearby, with views across the city, is named in his honour.