Born in Wairoa in 1939, Adsett attended Raupunga Native School where he first witnessed kōwhaiwhai painted around the doorway of an old whare. This artistic spark was kindled at Te Aute College, then with the Department of Education, where he received his formal training in Māori art from tohunga whakairo Pine Taiapa, developing his skills and knowledge of kōwhaiwhai to become one of the most influential contemporary Aotearoa New Zealand artists of his generation.
Adsett's paintings have featured in major national and international art exhibitions, including Te Ao Mārama: Seven Māori Artists at the Sydney Opera House Gallery (1986); Maori Artists in Africa, National Gallery of Zimbabwe (1987); Kohia ko Taikaka Anake, National Art Gallery of New Zealand (1990); Headlands: Thinking Through New Zealand Art, Museum of Contemporary Art, Sydney (1992); Te Waka Toi: Contemporary Māori Art; which toured to San Diego, Phoenix, Chicago, Seattle and Hawai'i (1992-94); Korurangi (1995), Auckland Art Gallery Toi o Tāmaki; Patua, Māori Arts in Action, City Gallery Wellington Te Whare Toi (1996); Kiwa-Pacific Connections, Spirit Wrestler Gallery, Vancouver (2003); and Toi Tū Toi Ora: Contemporary Māori Art, Auckland Art Gallery Toi o Tāmaki (2020).
Adsett was made a Member of the New Zealand Order of merit for his services to art in 2005. In 2006 he received his Master of Māori Visual arts Degree with First Class Honours from Massey University and was appointed adjunct professor at Te Wānanga o Aotearoa for his contribution to art education. In 2014 Adsett was awarded an honourary doctorate from Massey University and in the same year was presented with the Creative New Zealand Te Waka Toi Supreme Award Te Tohu Aroha mo Te Arikinui Dame Te Atairangi kaahu. In 2020 the Arts Foundation awarded him the Whakamana Hiranga Icon Award.
Hardcover, 160 pages, with full colour images of many of his works, prefaced and edited by Reuben Friend (Ngāti Maniapoto) of Pātaka Art+Museum in Porirua, New Zealand.