Te Wharepōuri, known as Te Kakapi-o-te-rangi in his youth, was born probably not long before 1800, and grew up in Taranaki. His mother was Hine-i-te-uru, senior wife of Te Whiti-o-Rongomai II, fourth child of Aniwaniwa, son of Te Whiti-o-Rongomai I and husband of Tāwhirikura. By the 1830s Hōniana Te Puni-kōkopu, a first cousin of Te Wharepōuri, was leader of those hapū to which Te Wharepōuri principally belonged – Ngāti Tāwhirikura and Ngāti Te Whiti of Te Āti Awa at Taranaki, Waikanae, Ōtaki and Te Whanganui-a-Tara (Wellington Harbour). By descent from Te Whiti-o-Rongomai II, Te Wharepōuri was the uncle of Te Whiti-o-Rongomai III, the prophet of Parihaka.
The times in which Te Wharepōuri lived were filled with exceptional tribal conflict, in which his role was that of a war leader. His talents and force of character led his hapū to regard him as their senior chief. He probably fought against the huge expedition of northern tribes in 1821–22. About 1822 he fought against Waikato in the great battle at Motunui. By the mid 1820s he was travelling and fighting further afield, perhaps with Te Whatanui in Hawke's Bay, and with Ngāti Tama and Ngāti Mutunga when they first tried to settle in Wairarapa. In 1828 he persuaded Jacky Love and his mate, Dicky Barrett, to set up their trading base at Ngāmotu, near present day New Plymouth. Te Wharepōuri travelled on Barrett's schooner, Tohora, to Sydney, in New South Wales, to purchase muskets and powder for the defence of his people against further invasions.
The Waikato people returned to Taranaki in 1831, to avenge their earlier defeats. Great numbers of Taranaki people were killed by Waikato at Pukerangiora, and many survivors took refuge with Te Wharepōuri at Ōtaka pā, Ngāmotu. Love and Barrett helped him when the pā was besieged, loading ships' guns with pieces of iron and stones. Waikato withdrew after three weeks, leaving over 350 dead.
Knowing that Waikato would seek revenge for this major defeat, Te Wharepōuri and other chiefs decided to migrate southwards to new homes far from their strongest enemies. About 1832 Te Wharepōuri led 400 fighting men, with their women and children, on the migration known as Tama-te-uaua. On this march his people were known as Ngāmotu, after their last place of residence; they included Ngāti Tāwhirikura and Ngāti Te Whiti. Other groups, under their own leaders, joined the migration: Puketapu, Manukorihi, Pukerangiora, Ngāti Rāhiri, Kaitangata, Ngāti Tū, Ngāti Hineuru, Ngāti Mutunga, Te Whakarewa and Ngāti Tama. Love and Barrett also went south, with their Te Āti Awa families.
Te Wharepōuri and his followers first went to Kāpiti, and then to Te Uruhi at Waikanae, where they stayed for two years. Some of the party, including his cousin Matangi, and his son Te Mānihera Te Toru, settled with their Ngāti Mutunga relatives at Pito-one (Petone). Later Te Wharepōuri moved to Te Koanga-ā-umu near Porirua, where Te Puni had cultivations. Then by canoe they went to Ōkiwi on the eastern shore of Te Whanganui-a-Tara and around the coast to Palliser Bay; they travelled northwards, past the Wairarapa lakes and up the Ruamāhanga River, always seeking a safe and permanent home.
At this time Wairarapa was almost entirely abandoned. Some years earlier Ngāti Tama and Ngāti Mutunga people from Taranaki had settled there, living uneasily with the tangata whenua, Rangitāne, Ngāti Kahungunu and Ngāti Ira. But after both sides had suffered defeats, the tangata whenua, led by Nuku-pewapewa and Pehi Tūtepākihirangi, had migrated north. Te Wharepōuri led his people into this nearly empty region. He settled where later Featherston was to be founded, and other Taranaki groups settled in other parts of Wairarapa. Te Wharepōuri, himself an expert canoe builder, set his people making canoes. They may also have taken part in whaling.
Nuku-pewapewa, on learning of this fresh Taranaki incursion, returned to Wairarapa with a war party, and attacked Te Wharepōuri at Tauwharerata. He escaped, but his wife, Te Uamairangi (or Te Urumairangi), and his niece, Te Kakapi, whom he regarded as his daughter, were captured. However, to make peace, Nuku-pewapewa saved their lives and offered them their liberty. In return, Te Uamairangi presented Te Kakapi to Nuku-pewapewa.
Te Uamairangi was sent with an escort to find Te Wharepōuri, but before she could do so he had reached Matiu (Somes Island, Wellington Harbour) in November 1835, just after the first contingent of Ngāti Mutunga had left for the Chatham Islands. Before this contingent left, Wiremu Piti Pōmare and others had formally transferred the mana over their lands in this region to Matangi and his son Te Mānihera Te Toru. Matangi invited Te Wharepōuri to visit Pito-one and prevailed on him to take possession of Ngāūranga, which Ngāti Mutunga had left. Though one of the occupying hapū, Ngāti Haumia, had been granted by Ngāti Mutunga the right to cultivate, Te Wharepōuri drove them out.
While he had been at Pito-one, his wife arrived. Te Wharepōuri saw the chance to make peace with at least some of Te Āti Awa's enemies. He protected Nuku-pewapewa's escort party, and began to raise crops to pay for passages to Hawke's Bay to redeem his niece.
At Ngāūranga, Te Wharepōuri (with Wī Tako Ngātata-i-te-rangi and others) cleared the bush and built a house, Te Akitiwha, for communal use. Later he built himself a separate house called Pukeatua. To keep his claims warm he returned at times to Wairarapa. He was at Palliser Bay when the whaling ship Active arrived in April 1836, and tried to capture the vessel, in order to join Ngāti Mutunga in the security of the Chatham Islands. But the ship's master managed to sail off with Te Wharepōuri and only 20 of his followers, and to land them in Queen Charlotte Sound.
Three years later Te Wharepōuri was living at Ngāūranga when the New Zealand Company ship Tory arrived. In just over one hectic week he and his cousin Te Puni carried through the sale of all the land between Rimurapa (Sinclair Head) and Tūrakirae, and from the sea to the summits of the Tararua Range. They did this partly from insecurity: no more Te Āti Awa were joining them and many Taranaki people had left. They also benefited greatly from the purchase price; at one stroke Te Wharepōuri acquired 120 muskets and 21 kegs of powder. Further, he and his fellow chiefs expected to be protected by the presence of the Europeans with their ships and guns.
The sale led to more fighting, however. Ngāti Raukawa were angered that Te Āti Awa had managed to acquire wealth by selling land which they felt was held by Te Āti Awa only on sufferance. The battle of Te Kūititanga was fought between them just three weeks after the sale. Te Wharepōuri was not present at the fighting, but arrived six days later ready to support his relatives. Peace was made in November.
Eventually Te Wharepōuri was in a position to go to Hawke's Bay to seek the return of Te Kakapi. But Nuku-pewapewa drowned while on his way to meet Te Wharepōuri, who recited a well known lament for him. Te Wharepōuri then began negotiations with Pehi Tūtepākihirangi. Te Wharepōuri offered greenstone, but Tūtepākihirangi would accept nothing less than the restoration of Wairarapa. Te Wharepōuri agreed, and persuaded most of his Taranaki allies. The Tararua Range became the boundary between the migrants from the north and the tangata whenua. Rangitāne, Muaūpoko and other kin of the Wairarapa people thus recognised the transfer of ownership of the land west of the Tararua range. A sandstone pillar to commemorate this peace was erected on the beach at Whakataki on the east coast.
Although William Wakefield, the leader of the New Zealand Company party, had told Te Wharepōuri that hundreds of settlers would be coming, he was staggered when they arrived. He had expected to have a trading centre with only a handful of Europeans under his protection and dependent on him. Instead, he found that the sale of the Wellington district meant that he had lost for ever his right to more than a fraction of his territory. At one point he planned to return to Taranaki, but in spite of his misgivings he remained close to the new settlement of Port Nicholson (Wellington) and signed the Treaty of Waitangi in April 1840.
Te Wharepōuri's last two years were not happy. The people living at Te Aro pā disputed the sale of the district, claiming that their share of the purchase goods was too small, and that it had been merely a present to Te Wharepōuri's sister who lived there. Wī Tako and his father at the other harbour settlements of Kumutoto and Pipitea were also not satisfied. There were also disputes at Ngāūranga, and over the reserves for Te Wharepōuri and his people. Te Wharepōuri's mana was fast disappearing. Settlers were leaving Pito-one (now known as Petone), which was within his and Te Puni's influence, and moving to Britannia, as Wellington's Thorndon was then known. While New Zealand Company officials continued to court and flatter him, Te Wharepōuri and other Māori could see that in the eyes of the governor and his officials he was regarded as a leader who had sold land to which he did not have any real claim.
There was more trouble a little over a year before Te Wharepōuri died. The body of a Māori was discovered on the flat behind Te Aro pā. Te Wharepōuri prevented an autopsy, and tried to convince his people that settlers were responsible for the murder. For some days the Europeans expected a massacre, and special constables were enrolled. But the attack did not take place.
Brooding over his wrongs and beset by troubles, Te Wharepōuri became haggard and thin. He was frequently drunk. He developed an abscess on his head, which proved incurable, and died on 22 November 1842 at Ngāūranga, survived by his wife, Te Uamairangi, and Te Kakapi. His body was taken to Petone for burial, and part of his canoe erected there as a memorial. On his deathbed he consigned the care of his people, both Māori and Pākehā, to his cousin Hōniana Te Puni-kōkopu.