Kingi Te Ahoaho Tahiwi was born on 1 December 1883 and baptised Te Kingi on 30 December at Rangiatea church, Otaki. His father, Rawiri Rota Tahiwi, a Native Land Court assessor, was of Ngati Raukawa, and of the hapu Ngati Maiotaki. His mother, Keita Koa, was also known as Kapu Meaha and Keita Pera. She was Te Arawa, and had connections with Ngati Whakaue, Ngati Pukaki, Ngati Tahu and Ngati Whaoa. Kingi Tahiwi had six full siblings and one half-sister, several of whom were also prominent leaders of his people. He was a namesake of his uncle, who was a signatory to the Treaty of Waitangi. He also used the name Kingi Rawiri Tahiwi.
He started his education at the Otaki state school, then attended Te Aute College from 4 March 1896. On matriculating in December 1901 he joined the school staff, and was a third assistant master in 1904. He became a licensed interpreter first grade on 27 October 1905, and from 1906 to 1913 worked for the Otaki office of the Wellington law firm Kirk and Wilson. He was secretary of the Otaki Domain Board in 1912. Kingi Tahiwi married Jane (Jean) Esther Armstrong of Ngai Tahu and Ngati Raukawa in Levin on 12 April 1909. They had a son, Kingi Te Ahoaho Gilling, and a daughter, Kahurangi Hera, and brought up a niece, Mereana Tahiwi.
Kingi Tahiwi's skills as an interpreter and translator formed the basis of his career. He was first appointed to the permanent staff of the Native Department as clerk and interpreter of the Waikato–Maniapoto District Native Land Court, Auckland, on 9 September 1915. He worked at the Aotea District Native Land Court, Wanganui, from 1920 to 1922, when he was appointed translator at the head office of the Native Department, Wellington. It was in this position that he became interpreter on many occasions to the prime minister and many members of Parliament. He attended national functions such as the 1934 visit to Rotorua of the duke of Gloucester, translating the duke's speech into Maori; and the opening of the Raukawa meeting house at Otaki in 1936, where he translated Prime Minister Michael Joseph Savage's speech into Maori and the Maori speeches into English. During the Second World War he censored letters written in Maori by members of the 28th New Zealand (Maori) Battalion. He continued at head office until his death, accumulating nearly 33 years' service in the Native Department (later the Department of Maori Affairs).
A rugby enthusiast, Kingi Tahiwi was the secretary of the Maori Advisory Board, formed in 1922, which he represented on the management and executive committees of the New Zealand Rugby Football Union from 1927 until 1948. He refereed in the King Country, Bay of Plenty and Horowhenua, and managed the 1932, 1934, 1935 and 1936 Maori All Black teams.
Raised in a musical family who were prominent in a Maori brass band and a choral society at Otaki, Kingi Tahiwi was a tenor in St Paul's Choir. In 1937 he founded the Ngati Poneke Young Maori Club, subsequently becoming chairman and choirmaster. He composed songs such as 'He puru taitama', 'To ringa e hine', 'Kaore he wahine', 'Takiri atu takiri mai', and 'E whiti te marama', and composed Maori lyrics for the Brahms lullaby. Some of his music was composed on a long-necked five-string banjo, then others would adapt the music for piano. During the war the Ngati Poneke Young Maori Club flourished. It provided a meeting ground for Maori in the capital, and held regular concerts for American servicemen. Tahiwi was also chairman of the Ngati Poneke tribal and Wellington executive committees.
Kingi Tahiwi was a Freemason from May 1929. In 1946 he was appointed OBE in recognition of his contribution to the organisation of the Maori war effort. His wife, Jane, died on 3 January 1942, and on 15 May 1946 at Wellington he married Elsie Winifred Loader (formerly Duley). There were no children of the marriage. Kingi Tahiwi died in Wellington on 20 December 1948 and was interred at Rangiatea cemetery, Otaki. He was survived by Elsie, his daughter and his niece. His son, an officer in the Royal New Zealand Air Force, was missing presumed killed in action during the Second World War.