Stewart was the son of Elizabeth Jane (née Clark) and John Stewart of Nairn. His father was a lawyer and director of Education in the city of Edinburgh. Stewart attended Edinburgh Academy, where Robert Louis Stevenson had been a pupil for a short time, and later studied English literature at Oriel College, Oxford. In 1929 he went to Vienna to study psychoanalysis. He was lecturer in English at the University of Leeds from 1930 to 1935, and then became Jury Professor of English in the University of Adelaide, South Australia.

He returned to the United Kingdom to become Lecturer in English at the Queen's University of Belfast from 1946 to 1948. In 1949 he became a Student (equivalent of Fellow in other Oxford colleges) of Christ Church, Oxford. By the time of his retirement in 1973, he was a professor of the university.

Using the pseudonym Michael Innes, he wrote about forty crime novels between 1936 and 1986. Innes's detective novels are playfully highbrow, rich in allusions to English literature and to Renaissance art. Sinuous, flexible and effortlessly elegant, Stewart's prose is refreshingly free of all influence by Strunk & White. The somewhat ponderous writing style and analysis of character, particularly in the early novels, is frequently Henry Jamesian.The best-known of Innes's detective creations is Sir John Appleby (originally Inspector John Appleby) of Scotland Yard, who is a feature of multiple books. Other novels also feature the amateur but nonetheless effective sleuth, painter and Royal Academician, Charles Honeybath. The two detectives meet in "Appleby and Honeybath." Some of the later stories feature Appleby's son Bobby as sleuth.

Stewart also wrote studies of Rudyard Kipling, Joseph Conrad, and Thomas Hardy. His last publication was his autobiography Myself and Michael Innes (1987).

In 2007, his estate transferred all of Stewart's copyrights and other legal rights to Owatonna Media. In 2010, the last of his previously uncollected stories appeared in Appleby Talks About Crime, from the specialist mystery publisher, Crippen & Landru.

J. I. M. Stewart

Critical works

• James Joyce (1957)
• Eight Modern Writers (1963)
• Thomas Love Peacock (1963)
• Joseph Conrad (1968)
• Shakespeare's Lofty Scene (1971)
• Thomas Hardy: A Critical Biography (1971)

Fiction

• Mark Lambert's Supper (1954)
• The Guardians (1955)
• A Use Of Riches (1957)
• The Man Who Won The Pools (1961)
• The Last Tresilians (1963)
• An Acre of Grass (1965)
• The Aylwins (1966)
• Vanderlyn's Kingdom (1967)
• Avery's Mission (1971)
• A Palace of Art (1972)
• Mungo's Dream (1973)
• A Staircase in Surrey quintet:
• The Gaudy (1974)
• Young Patullo (1975)
• Memorial Service (1976)
• The Madonna of the Astrolabe (1977)
• Full Term (1978)
• Andrew And Tobias (1980)
• A Villa in France (1982)
• An Open Prison (1984)
• The Naylors: a novel (1985)

Short Stories

• The Man Who Wrote Detective Stories (1959)
• Cucumber Sandwiches (1969)
• Our England is a Garden and other stories (1979)
• The Bridge At Arta and other stories (1981)
• My Aunt Christina: and other stories (1983)
• Parlour 4 and other stories (1984)

Memoir

• Myself And Michael Innes: A Memoir (1987)

As Michael Innes

Most of these works are Inspector Appleby novels. Exceptions are marked ?:

• Death At the President's Lodging (1936) (also known as Seven Suspects)
• Hamlet, Revenge! (1937)
• Lament for a Maker (1938)
• Stop Press (1939) (also known as The Spider Strikes)
• The Secret Vanguard (1940)
• There Came Both Mist And Snow (1940) (also known as A Comedy of Terrors)
• Appleby On Ararat (1941)
• The Daffodil Affair (1942)
• The Weight of the Evidence (1943)
• Appleby's End (1945)
• ?What Happened At Hazelwood (1946)
• ?From London Far (1946) (also known as The Unsuspected Chasm)
• A Night of Errors (1947)
• ?The Journeying Boy (1949)
• Operation Pax (1951) (also known as The Paper Thunderbolt)
• A Private View (1952) (also known as One-Man Show and Murder Is an Art)
• ?Christmas At Candleshoe (1953) (also known as Candleshoe)
• Appleby Talking (1954) (also known as Dead Man's Shoes) [short stories]
• The Man from the Sea (1955) (also known as Death By Moonlight)
• Appleby Talks Again (1956) [short stories]
• Old Hall, New Hall (1956) (also known as A Question of Queens)
• Appleby Plays Chicken (1957) (also known as Death On a Quiet Day)
• The Long Farewell (1958)
• Hare Sitting Up (1959)
• ?The New Sonia Wayward (1960) (also known as The Case of Sonia Wayward)
• Silence Observed (1961)
• A Connoisseur's Case (1962) (also known as The Crabtree Affair)
• ?Money from Holme (1964)
• The Bloody Wood (1966)
• A Change of Heir (1966)
• Appleby At Allington (1968) (also known as Death By Water)
• A Family Affair (1969) (also known as Picture of Guilt)
• Death At the Chase (1970)
• An Awkward Lie (1971), ISBN 0-396-06345-4
• The Open House (1972), ISBN 0-396-06524-4
• Appleby's Answer (1973), ISBN 0-396-06744-1
• Appleby's Other Story (1974), ISBN 0-396-06715-8
• The Mysterious Commission (1974), ISBN 0-396-07134-1
• The Appleby File (1975), ISBN 0-396-07279-8 [short stories]
• The Gay Phoenix (1976), ISBN 0-396-07442-1
• ?Honeybath's Haven (1977), ISBN 0-396-07555-X
• The Ampersand Papers (1978), ISBN 0-396-07663-7
• Going It Alone (1980), ISBN 0-396-07819-2
• Lord Mullion's Secret (1981), ISBN 0-396-08005-7
• Sheiks and Adders (1982), ISBN 0-396-08063-4
• Appleby And Honeybath (1983), ISBN 0-396-08247-5
• Carson's Conspiracy (1984), ISBN 0-396-08395-1
• Appleby And the Ospreys (1986), ISBN 0-396-08950-X
• Appleby Talks About Crime (2010) [short stories]

Christmas at Candleshoe was the basis for the 1977 film Candleshoe starring Jodie Foster, Helen Hayes and David Niven.