Gardner was born in Batavia, New York. His father was a lay preacher and dairy farmer, and his mother taught English at a local school. Both parents were fond of Shakespeare and often recited literature together. He was active in the Boy Scouts of America and made Eagle Scout. As a child, Gardner attended public school and worked on his father's farm, where, in April 1945, his younger brother Gilbert was killed in an accident with a cultipacker. Gardner, who was driving the tractor during the fatal accident, carried guilt for his brother's death throughout his life, suffering nightmares and flashbacks. The incident informed much of Gardner's fiction and criticism ... most directly in the 1977 short story "Redemption," which included a fictionalized recounting of the accident.

Gardner began his university education at DePauw University, but received his undergraduate degree from Washington University in St. Louis in 1955. He received his M.A. & PhD. in 1958 from the University of Iowa.

Gardner's best known novels include: The Sunlight Dialogues, about a brooding, disenchanted policeman who is asked to engage a madman fluent in classical mythology; Grendel, a retelling of the Beowulf legend from the monster's point of view with a philosophical underlaying; and October Light, about an aging and embittered brother and sister living and feuding together in rural Vermont. This last novel won the National Book Critics Circle Award in 1976. Each book features brutish, isolated figures struggling for integrity and understanding in an unforgiving society.

Gardner was a lifelong teacher of fiction writing. He was a favorite at the Bread Loaf Writers' Conference. His two books on the craft of writing fiction...The Art of Fiction and On Becoming a Novelist...are considered classics. He was famously obsessive with his work, and acquired a reputation for advanced craft, smooth rhythms, and careful attention to the continuity of the fictive dream. At one level or another, his books nearly always touched on the redemptive power of art.

In 1978, Gardner's book of literary criticism, On Moral Fiction, sparked a controversy that excited the mainstream media, vaulting Gardner into the spotlight with an interview on The Dick Cavett Show (May 16, 1978) and a cover story on The New York Times Magazine (July, 1979). His judgments of contemporary authors...including such luminaries of American fiction as John Updike and John Barth...which could be termed either direct, courageous, or unflattering, depending on one's perspective, harmed his relations with many in the publishing industry. Gardner claimed that lingering animosity from critics of this book led to the lukewarm critical reception of his final novel, Mickelsson's Ghosts. What was seemingly lost in the furor over On Moral Fiction was Gardner's central thesis: that fiction should be moral. Gardner meant "moral" not in the sense of narrow religious or cultural "morality," but rather that fiction should aspire to discover those human values that are universally sustaining. Gardner felt that few contemporary authors were "moral" in this sense, but instead indulged in "winking, mugging despair" (to quote his assessment of Thomas Pynchon) or trendy nihilism in which Gardner felt they did not honestly believe. Gore Vidal found the book, as well as Gardner's novels, sanctimonious and pedantic, and he called Gardner the "late apostle to the lowbrows, a sort of Christian evangelical who saw Heaven as a paradigmatic American university."

In 1994, Stewart O'Nan published On Writers and Writing a posthumous collection of Gardner's essays and reviews. His friend and former student Charles R. Johnson wrote the introduction.

Gardner inspired, and some say also intimidated, his writing students. At Chico State University, when Raymond Carver, who was almost 5-years younger, mentioned to Gardner that he had read, but not liked, the assigned short story, Robert Penn Warren's "Blackberry Winter", Gardner said, "You'd better read it again." "And he wasn't joking", said Carver, who related this anecdote in his foreword to Gardner's book On Becoming a Novelist. In that foreword, he makes it clear how much he respected Gardner, and also relates his extraordinary kindness.

Gardner spent the years just prior to his death as a professor at Harpur College of Binghamton University.

In 1977, Gardner published The Life and Times of Chaucer. In a review in the October 1977 issue of Speculum, Sumner J. Ferris pointed to several passages that were allegedly lifted either in whole or in part from work by other authors without proper citation. Ferris charitably suggested that Gardner had published the book too hastily, but on April 10, 1978, reviewer Peter Prescott, writing in Newsweek, cited the Speculum article and accused Gardner of plagiarism, insinuations that were met by Gardner "with a sigh."

On December 10, 1977, Gardner was hospitalized with colon cancer. He remained in Johns Hopkins Hospital for about a month and a half.

Gardner married Joan Louise Patterson on June 6, 1953; the marriage, which produced children, ended in divorce in 1980. Gardner then married the poet Liz Rosenberg in 1980, but this marriage also ended in divorce in 1982.

Gardner was killed in a motorcycle accident about from his home in Susquehanna County on Tuesday, September 14, 1982. State Police said that at about 2:30 PM, Gardner completed a curve on Route 92 about north of Oakland, when he lost control of his 1979 Harley-Davidson and went into the dirt shoulder, and then was thrown from the motorcycle. He was pronounced dead at Barnes-Kasson Hospital in Susquehanna. The crash came days before he was to marry Susan Thornton. Gardner is buried next to his brother Gilbert in Batavia's Grandview Cemetery.

Fiction

• The Resurrection (1966)
• The Wreckage of Agathon (1970)
• Grendel (1971)
• The Sunlight Dialogues (1972)
• Jason and Medeia (1973)
• Nickel Mountain (1973)
• The King's Indian (1974)
• October Light (1976)
• In the Suicide Mountains (1977)
• Vlemk the Box Painter (1979)
• Freddy's Book (1980)
• The Art of Living and Other Stories (1981)
• Mickelsson's Ghosts (1982)

Biography

• The Life and Times of Chaucer (1977)

Poems

• Poems (1978)

Children's stories

• Dragon, Dragon (and Other Tales) (1975)
• Gudgekin The Thistle Girl (and Other Tales) (1976)
• The King of the Hummingbirds (and Other Tales) (1977)
• A Child's Bestiary (1977)

Criticism and Instruction

• The Forms of Fiction (1962)
• The Construction of the Wakefield Cycle (1974)
• The Poetry of Chaucer (1977)
• On Moral Fiction (1978)
• On Becoming a Novelist (1983)
• The Art of Fiction (1983)

Translation

• The Complete Works of the Gawain Poet (1965)
• The Alliterative Morte Arthure and Other Middle English Poems (1971)
• Tengu Child (with Nobuko Tsukui) (1983)
• Gilgamesh (with John Maier, Richard A. Henshaw) (1984)

Essays and reviews

• On Writers and Writing (1994)