At the age of twelve Nan Chauncy moved to Tasmania with her family, setting up an orchard now called Chauncy Vale. She was heavily involved with the Girl Guides and taught English at a Danish Girl Guide finishing school during the 1920s and 1930s. While teaching English she began to write and after her return to Australia in 1938 she worked as a scriptwriter for the ABC.
Chauncy acted on her interest in children's literature and wrote the widely-admired book They Found a Cave (1948). Nine years later her second book, Tiger in the Bush, won the Book of the Year Award of the Children's Book Council, the first of several awards and nominations. Chauncy's books are highly regarded because they represent the first development in Australian children's literature toward a greater realism. Her books are primarily set in Tasmania. She was one of the first writers to portray the Tasmanian Aboriginal people with sympathy and dignity, and she expressed her conservationist concerns with stories that were committed to the natural beauty of the environment. Chauncy also wrote works of non-fiction for children. Chauncy also wrote an unpublished adult novel, 'Comfort Me with Apples'.
Many of Chauncy's novels have been translated and several have been adapted to other media. In 1962 They Found a Cave was produced as a feature film and Half a World Away (1962) was made into a television series in 1990. Chauncy Vale was gazetted as a conservation area in the 1940s and was bequeathed to the local council in 1988. Chauncy Vale Sanctuary attracts visitors interested both in conservation issues and the works of Nan Chauncy.
Nan Chauncy is the sister of Kay Chauncy Masterman. Rosenfeld was her married name until wartime antagonism caused her and her husband to change their surname to Chauncy, the family name of Nan's grandmother.