Born in Ashburton, New Zealand in 1927, Kāwharu attended Auckland Grammar School. He gained a BSc in geology and physics from the University of Auckland, an MA in anthropology from Cambridge University and an MLitt and DPhil from Oxford University.
In 1970 he became the foundation professor of social anthropology and Māori Studies at Massey University. Between 1985 and 1993 he was professor of Māori Studies and head of the Department of Anthropology at The University of Auckland, where he directed the building of the university's marae and was made an emeritus professor after he retired.
He was chair of the Ngāti Whātua o Ōrākei Māori Trust Board from 1978 to 2006. He served on the Royal Commission of the Courts (1976-1978), the New Zealand Māori Council, the Board of Māori Affairs (1987-1990) and the Waitangi Tribunal (1986-1996). He was a New Zealand delegate to UNESCO and a consultant to the United Nations Economic and Social Council (ECOSOC) and the Food and Agriculture Organization (FAO). He was also President of the Polynesian Society.
In the 1989 Queen's Birthday Honours Kāwharu was appointed as a Knight Bachelor for services to the Māori people. He was elected a Fellow of the Royal Society of New Zealand in 1994. In the 2002 Queen's Birthday and Golden Jubilee Honours Kāwharu was appointed to the Order of New Zealand.
Kāwharu died in Auckland in 2006.
- Ihaka, James (20 September 2006). "Ngati Whatua leader was a man of wisdom and knowledge". New Zealand Herald. Retrieved 13 January 2013.
- The London Gazette: . 16 June 1989. Retrieved 16 July 2012.
- "Sir (Ian) Hugh Kawharu". Royal Society of New Zealand. 2007. Retrieved 24 November 2013.
- "The Queen's Birthday and Golden Jubilee Honours 2002" (5 June 2002) 57 New Zealand Gazette 1553.