Mathers' family emigrated to Australia while he was a child. He attended state school in Sydney, and later Sydney Technical College, where he studied agriculture. He "farmed, clerked, woolled, gardened, landscaped, chemicalled", and did other things before settling into his writing career.
In 1961 he married and went to France to live in a cork oak forest. His two daughters were born in London. From 1964 he worked in Britain and Europe as a researcher. His first writing appeared in the early 1960s, and in 1967 he took up a writing fellowship in the United States. He returned to Australia in 1968.
Mathers completed his first novel, Trap, in 1966. It won the Miles Franklin Literary Award, an inventive and often comic novel concerning the escapades and family history of Jack Trap, an urban mixed-blood Aborigine in what was then a society racially divided by the White Australia Policy. His second novel, The Wort Papers (1972), ranged across the country in rural settings from the Kimberley to dairy country in northern New South Wales, and further established his reputation as a stylistic innovator and satirist.
Mathers wrote radio plays, articles and published many stories in magazines, journals and newspapers before beginning a substantial playwriting career. He lived in Melbourne for many years prior to his death in 2004.
- "Classic Australian Works". Sydney University Press. Retrieved 19 August 2008.
- Williams, Michael (15 January 2005). "Missing the point by Miles". The Age. Retrieved 19 August 2008.
- "Jack Trap is an awe-inspiring mixture of Irish, English, Aborigine, and even Tierra del Fuegan. But he looks Aboriginal. Admired by a few, hated by many, he is needed by more than care to admit it. Trap affects everyone. He is a shifting product of the back streets, passively resisting poverty and racialism, occasionally indulging in bursts of aggression. Peter Mathers knows Trap, as he knows his background. Out of Trap he has fashioned Trap the symbol - around which lurk a variety of characters who represent the different aspects of an oppressive society. There are entertaining tales of his unlikely forebears; his father Wilson, who was unlucky enough to look white; his grandmother from South America; and his cedar-cutting grandfather, Armstrong Irish Trap. Peter Mathers deals gently with the underdog, reserving his most vitriolic satire for the affluent conformists. His original style and humour make Trap a biting, very funny novel." (From the dustjacket of the first edition)
- From a commentary published on goodreads.com: "Difficult can be good. Enormous fun. A uniquely Australian book about mid-20th century rural life and big business. Full of politics and satire and comic, romping scenarios and literary fireworks. This is one of the funniest novels written, anywhere; inventive, clever, witty, ribald, experimental ... it has many strengths but I recall talking to the author in 1997 and he indicated he wanted to re-edit it; he told me the book was produced in a hurry amid a corporate sell-out, and has never received adequate attention in editing."