Peter McIntyre was born in Dunedin. His father, a lithographic artist, founded Dunedin's Caxton Printing Company. Young McIntyre attended Otago Boys' High School and the University of Otago. He studied painting under Dunedin artist Alfred O'Keeffe. McIntrye left New Zealand to study at London's Slade School of Art from 1931 until 1934. He worked in Britain as a free-lance artist until enlisting in 1939 with the 34th Anti-Tank Battery, a New Zealand unit formed in London. In 1941 whilst serving in Egypt, he was appointed as New Zealand's official war artist by Major General Freyberg. From 1941 to 1945 McIntyre recorded action in Crete, North Africa and Italy. His work was exhibited in New Zealand and Europe and reproduced in magazines such as the Illustrated London News and the New Zealand Listener. His work from this period belongs to the collection of war art at the National Archives in Wellington. Returning to New Zealand in 1946 McIntyre began a long and illustrious post war career. He lived and exhibited in Wellington, frequently undertaking painting trips abroad. In 1962 A H & A W Reed published The Painted Years, the first of eight books he would illustrate and write between then and 1981.
In 1970 McIntyre was awarded an OBE. A retrospective exhibition of McIntyre's war paintings was held at the City Gallery in Wellington in 1995. Opening on 22 July, the show had been visited by more than 22,000 people when the artist died in Wellington on 11 September. Today he is recognised as one of New Zealand's most important landscape artists.