Ngata practised as a lawyer before entering politics in 1897, when he established the Young Māori Party alongside numerous alumni of Te Aute College, including future fellow cabinet minister Māui Pōmare.

At the age of 69 he returned to his Ngāti Porou home 129 kilometres north of Gisborne, where he lived with his four sons and four daughters, and multiple grandchildren, until his death seven years later.

[1][2] Ngata was born in Te Araroa (then called Kawakawa), a small coastal town about 175 km (109 mi) north of Gisborne, New Zealand.

His father was Paratene Ngata, a tribal leader and expert in traditional lore, and his mother was Katerina Naki, the daughter of an itinerant Scot, Abel Enoch.

[1] Ngata was greatly influenced both by his father and by his great-uncle Ropata Wahawaha (who had led loyal kūpapa Ngāti Porou forces against their Pai Mārire enemy (commonly known as Hauhau) in the East Cape War and later Te Kooti's escapees from the Chatham Islands).

[5] In 1895, a year before finishing his second degree (law), Ngata married 16-year-old Arihia Kane Tamati who was also of the Ngāti Porou iwi.

[3] Shortly after Ngata's legal qualifications were recognised, he and his wife returned to Waiomatatini where they built a house, initially called 'Te Wharehou' and later known as 'The Bungalow'.

[1] Ngata quickly became prominent in the community, making a number of efforts to improve the social and economic conditions of Māori across the country.

At the same time, he gradually acquired a leadership role within Ngāti Porou, particularly in the area of land management and finance.

Ngata's first involvement with national politics came through his friendship with James Carroll, who was Minister of Native Affairs in the Liberal Party government.

Ngata assisted Carroll in the preparation of two pieces of legislation, both of which were intended to increase the legal rights enjoyed by Māori.

In the 1905 election, Ngata himself stood as the Liberal candidate for the Eastern Maori electorate, challenging the incumbent Wi Pere.

[citation needed] In late 1909, Ngata was appointed to Cabinet, holding a minor ministerial responsibility for Māori land councils.

[citation needed] In the First World War, Ngata was highly active in gathering Māori recruits for military service, working closely with Reform Party MP, Maui Pomare.

In 1934, during the depression, the public, media and parliament became alarmed at the large sums of money being gifted to Te Puea and others.

A royal commission was held and Ngata was found guilty of irregularities in expenditure and negligence in administration, but no major scandals were unearthed.

It was also alleged that Ngata had shown favouritism to Ngāti Porou and Waikato, especially Te Puea and her husband Rawiri Tumokai Katipa.

Bob Semple, a leading Labour politician, said the Royal Commission investigation showed one of the worst specimens of abuse of political power, maladministration, misappropriation of public funds as well as a betrayal of trust.

Ngata, while denying any personal wrongdoing, accepted responsibility for the actions of his department and was dismissed from his ministerial position.

On 22 June 1950, he was appointed to Parliament's upper house, the Legislative Council, but was too ill by this time to take his seat.

His image has appeared on the New Zealand fifty-dollar note since 1999 along with Porourangi Meeting House, which is significant as it is located next to the original Ngata family home and Waiomatatini Marae, near Ruatōria.

While many have praised him for tireless work to promote the Māori language (especially in a white-based, right-wing political environment), others have criticised and even derided him for corruption, conservatism and not taking the views of all his iwi into account while making incredibly important decisions on his own.