Tāmihana, the son of Te Rauparaha, was also known as Katu in his youth. Along with his father, he signed Te Tiriti at Kāpiti on 14 May 1840. Whereas his father signed with a mark from his moko, Tāmihana wrote his own name.
In 1841 he converted to Christianity and took the name Tāmihana (Thompson). In 1842–43 he and Mātene Te Whiwhi (the next signatory) travelled round Te Waipounamu, preaching the Christian message to their former enemies, Ngāi Tahu.
In 1850–52 he travelled to England and was presented to Queen Victoria. Upon returning home he sought to establish a monarchy for the Māori people. He supported the King movement’s attempts to halt the sale of Māori land but withdrew his support when the Kīngitanga sided with Wiremu Kīngi Te Rangitāke in the 1860–61 Taranaki War.
In his later years he ran a farm near Ōtaki and was heavily involved in Native Land Court business.