Tomoana was born in the 1820s or early 1830s, probably in Heretaunga, Hawke's Bay. He was the third son of Te Rotohenga, also called Winipere, from whom he derived his high rank. Her father was Hāwea of Ngāti Te Whatu-i-āpiti, heir to mana over Heretaunga, and eponymous ancestor of Ngāti Hāwea, an important hapū of Te Awanga and Heretaunga. Tomoana's father, Hira Te Ota, was a descendant of Tamatai and Te Rēhunga. Tomoana's younger brother was Pene Te Uamairangi; his elder half-brothers were Karaitiana Takamoana and Te Meihana Tākihi. Ngāti Hāwea was his principal hapū. He was also connected to Ngāti Hinetāhu through his maternal grandmother, Ringahora, to Ngāti Te Rēhunga through his father, and to Ngāti Hōri.
Little is known of Tomoana's early life or education. During his childhood, wars were fought to drive invaders out of Heretaunga, and many of his people took refuge at Māhia Peninsula, returning to Heretaunga after 1838. By 1852 he had become a Christian, taking the name Hēnare (Henry) at baptism, and had married twice. His second wife, whom he married on 18 October 1852, is believed to have been Ātaneta Rukarei. They had no children. His third wife, Ākenehi (Agnes) Pātoka, is said to have borne 13 children, only two of whom survived Tomoana.
In 1851 Tomoana, his father and brothers had signed deeds for the sale of the Ahuriri and Waipukurau blocks to the Crown. Tomoana also took part in the sale of the Matau-a-Māui (Cape Kidnapper) block in 1855. In 1856 he joined Takamoana and other chiefs in a struggle to check the land-selling activities of Te Hapūku. The same year he joined an armed 'survey' which accompanied the district commissioner, G. S. Cooper, to the boundaries of lands they claimed. He fought against Te Hapūku in the 1857–58 war at Te Pakiaka, near Whakatū.
Despite his stand against Te Hapūku, in the 1860s Tomoana himself became involved in a ruinous course of leasing and selling land, largely because of his growing debts to European storekeepers. About 1867 he sold the Wahaparata block, and Cooper reported that he and other chiefs were 'selling away at a great rate…they will soon be paupers'.
In 1864 Tomoana had leased the Heretaunga block of over 17,000 acres to Thomas Tanner for 21 years, at an initial rental of £600 per annum. In 1867 that illegal lease was replaced after the block and the adjoining Tarakaihae block had been surveyed, the latter at Tomoana's order, and had passed through the Native Land Court. Te Hapūku requested that the Heretaunga block be subdivided between Ngāti Kahungunu and Ngāti Te Rēhunga, but Tomoana objected, saying that he was a claimant on both sides. At least one witness was willing for the whole block to be granted to Tomoana and Takamoana, but they became only two of 10 grantees; the others were almost all leading Heretaunga chiefs or their heirs.
Tomoana and Takamoana intended to retain Heretaunga as tribal property. They regarded themselves as trustees for 16 hapū comprising hundreds of individuals. But land law had the effect of making the 10 grantees the absolute owners of their shares. Tanner and his associates, fearing the competition of other would-be purchasers, began to use the pressure of the grantees' debts to acquire their shares. According to Tanner, once the shares had begun to go, Tomoana encouraged him to acquire Tāreha Te Moananui's interest.
While pressure was mounting on Tomoana to sell his share of Heretaunga, Te Kooti Arikirangi Te Tūruki had escaped from the Chatham Islands with nearly 300 followers. Tomoana, following Takamoana's policy, had always been a supporter of the government; he had probably fought against the Hauhau at Ōmarunui in 1866. Now he joined in the pursuit of Te Kooti, leading a contingent of Ngāti Kahungunu up the Ruakituri River, Wairoa, in August 1868, where he succeeded in crossing a difficult ford under fire and forcing Te Kooti to retreat. In October he led the Heretaunga contingent with Tāreha and other chiefs in an abortive advance on Puketapu pā. Following Te Kooti's attack on Poverty Bay in November, Tomoana fought at Mākāretu, helping to take the pā on 3 December.
In 1869 Tomoana raised another troop to pursue Te Kooti into the Taupō district. As he was about to leave he was served with a writ for £900 in debts. On 9 September at Tauranga-Taupō Tomoana's troop was attacked without warning, but defended themselves well. On 25 September he led his men in driving Te Kooti from Te Ponanga near Lake Rotoaira, and at Te Pōrere on 4 October he was the Ngāti Kahungunu leader against Te Kooti's redoubt. Te Kooti, although wounded, escaped, and the following morning Tomoana was sent out with a small force to track him. After two unsuccessful searches, he and his company were ordered to return to Napier because of lack of supplies.
For his campaigns against Te Kooti, Tomoana (who had been commissioned as a captain of militia) received a sword of honour. But J. D. Ormond, the Hawke's Bay superintendent, had refused him regular pay on the pretext that the government could not afford it, and Tomoana was even deeper in debt, at least some of which was probably incurred in equipping his men. By December 1869 he owed more than £3,000. It was alleged that Tomoana had agreed that the Heretaunga block would have to be sold to pay his debts. Tomoana and Takamoana denied that they had agreed to sell, but by 6 December they had signed a contract. A secret agreement was made to pay Tomoana and Takamoana additional annuities for 10 years.
On 15 or 16 December 1869, while Takamoana was in Auckland attempting to obtain financial help from Donald McLean, the native minister, Tomoana signed a conveyance of his share. He claimed he was tricked into visiting Tanner's solicitor and once there was held against his will and forced to sign. A fresh conveyance was prepared a few months later and Heretaunga changed hands. Tomoana received the greatest share of the money, but it all went to pay his debts. He retained a 10th share of the Karamu reserve, but disputes dogged this block for decades.
In February 1870 Tomoana again offered to march against Te Kooti, but most of his people refused to follow unless they were offered regular pay. By mid 1870 he was inclined to seek a new solution to land problems. After a visit from Tomoana, Ormond reported to McLean in August 1870 that 'undesirable feeling [was] gaining ground'. He fancied that 'the loss of their lands must be at the bottom of it.'
The 'undesirable feeling' blossomed into what became known as the Hawke's Bay Repudiation movement. By June 1872 the repudiation of past land agreements occupied the attention of most Hawke's Bay Māori. Ormond considered a 'collision' imminent. But it did not take place, as Tomoana and Takamoana were not yet fully committed to the movement. At a meeting at Pākōwhai in July Tomoana opposed Hēnare Matua's plan to sweep away past transactions, and proposed instead to take all land grievances to Wellington. Takamoana promised that if the government did not appoint a commission to inquire into land grievances he would join the repudiationists.
A commission of inquiry was appointed, but it was a great disappointment. Many claims were not heard, no action was or could be taken, and the commission found that mortgages and the acquisition of tribal property through pressure on indebted grantees were legitimate actions. From April 1873 Tomoana was fully committed to repudiation. He attended a secret meeting at Pakipaki whose main aims were to get up a monster petition demanding a new commission with greater powers, and to work for a change of government. The Auckland lawyer John Sheehan was to help them to carry out their plans.
Tomoana's greatest contribution to repudiation was to set up, publish and edit a Māori newspaper called Te Wānanga, at Pākōwhai. The first issue emerged on 5 August 1874; it continued, usually weekly, until December 1878. From sometime in 1875 it was edited by John White. The first few numbers, in Māori only, contained Tomoana's explanations of the paper's purpose. It was hoped to educate its readers about European business practices, and provide contact between Māori and Pākehā concepts. It would unite the tribes. The paper discussed land selling and leasing, mortgages, reserves and Crown grants. It proclaimed that Takamoana, now MHR for Eastern Māori, was the only true representative of Māoridom, claiming that other Māori members of Parliament had become the paid lackeys of the government. Controversial land cases were reported, many of which concerned Tomoana.
In the 1876 parliamentary election Tomoana canvassed the Waiapu district for Takamoana, whose victory, upheld despite a government challenge, was regarded as a triumph for Sir George Grey and for the Repudiation movement. In June 1876 an important meeting of chiefs was held at Pākōwhai. Tomoana was its host and a prime mover. The meeting expressed loyalty to the Queen, but called for unification of the tribes, yearly meetings of chiefs, an increase in Māori members of Parliament, and the reform of Māori land law. Tomoana displayed the same realism he had demonstrated in 1872. He argued for the continuance of the Native Land Court, and suggested that fuller use be made of existing protective clauses in Māori land law, saying that Parliament was unlikely to accept new proposals. He was supported by his brother and Hēnare Matua, and advised by John Sheehan, soon to be native minister.
Tomoana's reputation had made him the natural successor to Takamoana in the Eastern Māori seat in 1879. He defeated both the more radical Hēnare Matua and Ieni (Hans) Tapsell in this and the succeeding election. But as Grey and Sheehan's ministry progressed, Tomoana became increasingly disillusioned with them. In 1879 he created a sensation by voting against them in a vote of no-confidence. In the confused politics of 1879 Tomoana was for 17 days a member of the Executive Council in the Hall–Whitaker administration.
As an ordinary member of Parliament he made little impact. Like other contemporary Māori members he was hampered by a lack of fluent English, but he gained valuable experience in parliamentary procedure and Pākehā politics. In 1882 he succeeded in getting through to its second reading a bill to set up local Māori committees with power to adjudicate on land titles. This bill led directly to the 1883 Native Committees Act which gave committees the authority to advise the Native Land Court, and to arbitrate between Māori disputants in some matters if the disputing parties consented. Because they were regional rather than tribal and had insufficient powers, these committees were not acceptable to most Māori, but they were a step – albeit shortlived – towards self-determination.
As a member of the House Tomoana's influence among Māori was enhanced. He was sometimes called on to resolve disputes. In 1880 he intervened in a land dispute between Ngāti Rākaipaaka of Nūhaka and Ngāti Hine of Whakakī and was able to arrange a temporary peace in which discussions could continue. He intervened with less immediate success in a land dispute between John Harding and Heta Tiki of Waipāwa, but the case was eventually resolved in favour of the Māori owners.
In the 1884 election Tomoana was defeated by Wī Pere, but his mana as a chief and leader in Hawke's Bay was undiminished. In 1886, with Rēnata Kawepō, he set up a meeting in Hastings to discuss the forthcoming Native Land Administration Bill with John Ballance, the native minister. Tomoana was the first Māori spokesman. He reviewed past land legislation, concluding that all of it had brought harm to Māori, and asked that they be given more control over their affairs. Ballance's Native Land Administration Act 1886 established block committees, but they were generally regarded with suspicion, partly because it was feared that the proceeds of the land would be swallowed up in the committees' costs.
The death of Rēnata Kawepō in 1888 left Tomoana the senior Heretaunga chief of his generation. In May 1891 in Waipāwa he gave evidence to the Native Land Laws Commission, pointing out that great injustices had resulted from laws imposed on Māori by the European-dominated Parliament, and asking that Māori be allowed to make their own laws. This request reflected Tomoana's growing involvement with Te Kotahitanga, the movement for an independent Māori parliament. Hāmiora Mangakāhia, several times premier of the Māori parliament, credited Tomoana with being one of the principal agents of its establishment. As chairman of the Waipatu marae committee, Tomoana welcomed Kotahitanga members to the June 1892 session there. His parliamentary skills were put to good use; he was elected Speaker of the Great Council of Te Kotahitanga. He was elected again in 1893, but resigned after a few days. He served as Speaker on subsequent occasions, but by the fourth session regarded himself as 'leader of the opposition' in the Kotahitanga parliament. There were no organised parties within the movement, but his chosen role was to provide opposing arguments on debated issues.
Tomoana's greatest achievement as a member of Te Kotahitanga was to present to the native minister in June 1893 a draft Federated Māori Assembly Empowering Bill, and a petition listing Māori grievances. The bill asked for power over Māori to be delegated to Te Kotahitanga, subject only to the governor. In 1893 Tomoana took up the cause of Tūhoe who were resisting the survey of their land, and circulated a petition on their behalf throughout Hawke's Bay. This action led Premier Richard Seddon to release Tūhoe prisoners. In the 1898 session of the Kotahitanga parliament at Pāpāwai, Wairarapa, the main item of business was discussion of Seddon's bill to set up Māori land boards, which threatened to further reduce Māori control of their land. Tomoana took, as always, a moderate line, accepting the bill as a basis for discussion where most others regarded it as a violation of the rules and procedures of the Māori parliament.
Tomoana's moderation was rewarded. In June 1898 he was made a member of the Legislative Council, a position which he retained until his death on 20 February 1904. Thousands paid their respects to him at his tangihanga, and several hundred people attended his funeral at Waipatu, where he was buried in a vault close to the Anglican church. His mourners included Seddon and the minister of native affairs, James Carroll. He was survived by two children, including his eldest son, Paraire Tomoana. In 1911 a monument at Waipatu cemetery was unveiled to the memory of Hēnare Tomoana and his younger brother, Pene Te Uamairangi.