Dunn was born in Ashburton in Mid Canterbury, and attended Canterbury School of Fine Arts (Ilam), graduating with a degree in painting.He was awarded the Painting Prize in 1963.
He was appointed Head and Dean of the university's Elam School of Fine Arts in 1994.
He retired in 2006, at which point he was given the title of Emeritus Professor of Fine Arts.
[3] Dunn has written or co-written many books and monographs, predominantly on New Zealand art and in particular the artist Gordon Walters and his koru series of paintings initiated by the work Te Whiti in 1966.
An archive of his writing and related papers is held by the Auckland Art Gallery.