Tamihere gained arts and law degrees from the University of Auckland, being the first person in his family to attend university. After graduating, he became a lawyer, eventually working for the Māori Land Court and the Department of Māori Affairs. In 1991, Tamihere became the chief executive of the Waipareira Trust, a trust that provides health and education services to Māori in the Auckland region. He also served as chairman of the New Zealand Māori Rugby League Board. Tamihere had a relatively high profile before entering politics, having been selected as Person of the Year by "The Sunday Star-Times", New Zealander of the Year by "North & South" magazine, and Man of the Year by "Metro" magazine.