She was born in London, England in 1893 as Pérrine Millais. She was the grand daughter of the painter Sir John Millais, one of the founders of the Pre-Raphaelite Brotherhood. She spent her early life living in London, Brussels and in Perthshire in Scotland. She married Captain Malcolm Moncrieff, a veteran of the Boer War, in 1914. They moved from Britain to New Zealand after the end of the First World War where they settled at Nelson, having originally planned to move to Canada. She was the first female President of the Royal Australasian Ornithologists Union (RAOU), 1932–1933. She first joined the organisation in 1923 and two years later published "New Zealand Birds and How to Identify Them". The book was a success, with six editions published from 1923 through to 1961.
She is credited with being almost single-handedly responsible for setting aside land that would eventually be the Abel Tasman National Park. Pérrine was awarded the Loder Cup in 1953. In the 1975 Birthday Honours, she was appointed Commander of the Most Excellent Order of the British Empire (CBE) for "services to conservation as a naturalist and to the Abel Tasman National Park". The government of the Netherlands awarded her the Order of Orange-Nassau in 1974, in recognition of her efforts to protect Abel Tasman NP, an area of significant importance in the history of Dutch exploration.
Books she authored include:
- Moncrieff, P. (1925). New Zealand Birds and How to Identify Them. Whitcombe & Tombs: Auckland. (Field-guide. 5 editions published to 1961).
- Moncrieff, P. (1965). People Came Later. Author: Nelson.
- Moncrieff, P. (1976). The Rise and Fall of David Riccio. Ambassador: Wellington.
- Robin, Libby. (2001). The Flight of the Emu: a hundred years of Australian ornithology 1901-2001. Carlton, Vic. Melbourne University Press. ISBN 0-522-84987-3
- Hodge, Robin. "Pérrine Moncrieff". Dictionary of New Zealand Biography. Ministry for Culture and Heritage. Retrieved 2 January 2015.
- Secker, HL (1980). "Obituary. Perrine Millais Moncrieff". Emu. 80 (3): 171. doi:10.1071/mu9800171.
- Young, David (2004). Our Islands, Our Selves. Dunedin: University of Otago Press. ISBN 1-877276-94-4.
- "No. 46595". The London Gazette (Supplement). 6 June 1975. p. 7406.