Sidney Hudson Courtier attended school in Bendigo, where his father was a mine manager. These early experiences would supply the setting for several of his mystery novels. As a child, the writer who made the strongest impression on him was Robert Louis Stevenson, whom Courtier credited as having influenced his writing.

In 1933 Courtier married Audrey George; he served in the Army during the Second World War. He worked as a schoolteacher in rural Victoria, and was later a principal in Melbourne schools for teacher training for most of his life, and retired in 1969.

Courtier began his writing career in 1932, with the publication of a short story entitled As by Fire. He went on to write numerous articles and short fiction published in magazines and newspapers, including Argosy in the USA, and the Australian Journal and the Bulletin in Australia. Under various pseudonyms, he published twenty-six novels set in various Australian settings. Courtier was primarily a crime writer, but wrote three science fiction novels: Who Dies for Me?, Into the Silence, and The Smiling Trip.

Courtier was president of the Melbourne branch of International PEN, the world association of writers, in the 1945-57 and 1958-61 periods.

In 1967 Courtier suffered a stroke, which resulted in a loss of speech and movement abilities. According to Derham Groves, he taught himself to speak again using a series of speech exercises devised by himself. Later he tried to have these published, but this did not eventuate. His experiences informed his subsequent writing, as he went on to write about sensory loss in four of his crime novels: the loss of movement in No Obelisk for Emily (1970), the loss of memory in Dead If I Remember (1972), the loss of hearing in Into the Silence (1973), and the loss of sanity in The Smiling Trip (1975).

Courtier's mysteries are structured around puzzles, clues, and ciphers. He created three detectives: the debonair Superintendent Ambrose Mahon (Sydney C.I.B.), who features in six of his novels, Inspector C. J. 'Digger' Haig (Brisbane C.I.B.), who appears in seven, and Senior Detective Charles Bury (Melbourne). Two of his mystery novels, Death in Dream Time and The Glass Spear, are set in the bush and depict Aboriginal characters and ceremonies. His novels were published in Australia, the UK, and USA, and have been translated into French, German, and Japanese.