Internationally known and renowned writer and illustrator of fiction and non-fiction, Ingpen studied art and illustration under Harold Freedman at the RMIT from 1955-1958. He worked as a graphic designer at CSIRO from 1958 to 1967 before freelancing as a designer, illustrator, writer and consultant.
As well as working in the field of book illustration, Ingpen was also involved in the design of many major projects including stamps for the Captain Cook Bicentenary and the 50th anniversary of CSIRO, the Northern Territory flag and coat of arms, the Swan Hill Pioneer Settlement, and the Dromkeen Medal. He has painted murals and designed materials for United Nations projects and designed a tapestry commemorating the 150th anniversary of the MCG. The story of the tapestry, woven by members of the Victorian Tapestry Workshop, was told in a book The Tapestry Story : Celebrating 150 Years of the Melbourne Cricket Ground (Lothian Books, 2003). He was one of the founders of the Australian Conservation Foundation.
Ingpen was commissioned to undertake the illustrations for new editions of several classic children's works published by Walker Books including Around the World in Eighty Days (2000), Peter Pan and Wendy (2004), The Ugly Duckling (2005), Treasure Island (2005), The Jungle Book (2006), The Wind in the Willows (2007), Charles Dickens' s A Christmas Carol with 'A Christmas Tree' (2008), Alice's Adventures in Wonderland (2009), The Adventures of Tom Sawyer (2010), The Secret Garden (2010) and The Wonderful Wizard of Oz (2011).
Ingpen's work reflects his exploration of fantasy and the imagination and his interest in heritage and the environment. The landscapes and portraits in his illustrations are equally powerful. He co-authored with Michael Page (q.v.) the Encyclopedia of Things That Never Were (1985), republished as Out of This World: The Complete Book of Fantasy (1989).
In 2024, Ingpen illustrated The Hidden World of Mythical Folk by British author, Maz Evans.