McCarthy was born in Providence, Rhode Island on July 20, 1933, one of six children of Gladys Christina (née McGrail) and Charles Joseph McCarthy. His family were Irish Catholics. In 1937, the family relocated to Knoxville, where his father worked as a lawyer for the Tennessee Valley Authority. The family first lived on Noelton Drive in the upscale Sequoyah Hills subdivision, but by 1941 had settled in a house on Martin Mill Pike in South Knoxville (this latter house burned in 2009). McCarthy would later say “We were considered rich because all the people around us were living in one- or two-room shacks.” Among his childhood friends was Jim Long (1930–2012), who would later be depicted as J-Bone in Suttree.

In 1951, he began attending the University of Tennessee but dropped out in 1953 to join the Air Force. While stationed in Alaska, McCarthy voraciously read books, which he claimed was the first time he had done so. He also hosted a radio show. He returned to UTK in 1957, where he published two stories, “A Drowning Incident” and “Wake for Susan” in the student literary magazine, The Phoenix, writing under the name C. J. McCarthy, Jr. For these, he won the Ingram-Merrill Award for creative writing in 1959 and 1960. But in 1959, he dropped out of UTK for the final time and left for Chicago.

Since 1958, McCarthy has written all of his literary work and correspondence with a mechanical typewriter. He originally used a Royal but went looking for a more lightweight machine ahead of a trip to Europe in the early 1960s. He bought a portable Olivetti Lettera 32 for $50 at a Knoxville pawn shop and typed about five million words over the next five decades. He maintained it by simply “blowing out the dust with a service station hose.” Book dealer Glenn Horowitz said the modest typewriter acquired “a sort of talismanic quality” through its connection to McCarthy’s monumental fiction, “as if Mount Rushmore was carved with a Swiss Army knife.” His Olivetti was auctioned in December 2009 at Christie’s, with the auction house estimating it would fetch between $15,000 and $20,000. It sold for $254,500, with proceeds donated to the Santa Fe Institute. McCarthy replaced it with an identical model, bought for him by his friend John Miller for $11 plus $19.95 for shipping.

After marrying fellow student Lee Holleman in 1961, McCarthy “moved to a shack with no heat and running water in the foothills of the Smoky Mountains outside of Knoxville”. There the couple had a son, Cullen, in 1962. When writer James Agee’s childhood home was being demolished in Knoxville that year, McCarthy took bricks from the site and with them built one or more fireplaces inside his Sevier County shack. While caring for the baby and tending to the chores of the house, Lee was asked by Cormac to also get a day job so he could focus on his novel writing. Dismayed with the situation, she moved to Wyoming, where she filed for divorce and landed her first job teaching.

Random House published McCarthy’s first novel, The Orchard Keeper, in 1965. He had finished the novel while working part-time at an auto-parts warehouse in Chicago. McCarthy decided to send the manuscript to Random House because “it was the only publisher [he] had heard of.” At Random House, the manuscript found its way to Albert Erskine, who had been William Faulkner’s editor until Faulkner’s death in 1962. Erskine continued to edit McCarthy’s work for the next 20 years. Upon its release, critics noted its similarity to the work of Faulkner and praised his striking use of imagery. The Orchard Keeper won a 1966 William Faulkner Foundation Award for notable first novel.

In the summer of 1965, using a Traveling Fellowship award from The American Academy of Arts and Letters, McCarthy shipped out aboard the liner Sylvania hoping to visit Ireland. While on the ship, he met Englishwoman Anne DeLisle, who was working on the Sylvania as a dancer and singer. In 1966, they were married in England. Also in 1966, he received a Rockefeller Foundation Grant, which he used to travel around Southern Europe before landing in Ibiza, where he wrote his second novel, Outer Dark (1968). Afterward he returned to the United States with his wife, where Outer Dark was published to generally favorable reviews.

In 1969, the couple moved to Louisville, Tennessee, and purchased a dairy barn, which McCarthy renovated, doing the stonework himself. The couple lived in “total poverty”, bathing in a lake. DeLisle claimed, “Someone would call up and offer him $2,000 to come speak at a university about his books. And he would tell them that everything he had to say was there on the page. So we would eat beans for another week.” While living in the barn, he wrote his next book, Child of God (1973), based on actual events. Like Outer Dark before it, Child of God was set in southern Appalachia. In 1976, McCarthy separated from Anne DeLisle and moved to El Paso, Texas.

In 1974, Richard Pearce of PBS contacted Cormac McCarthy and asked him to write the screenplay for an episode of Visions, a television drama series. Beginning in early 1975, and armed with only “a few photographs in the footnotes to a 1928 biography of a famous pre-Civil War industrialist William Gregg as inspiration,” he and McCarthy spent a year traveling the South in order to research the subject matter. McCarthy completed the screenplay in 1976 and the episode, titled The Gardener’s Son, aired on January 6, 1977. It was also shown in numerous film festivals abroad. The episode would go on to be nominated for two primetime Emmy awards in 1977.

In 1979, McCarthy published the semi-autobiographical Suttree, which he had written over a period of 20 years. It was based on his experiences in Knoxville on the Tennessee River. Jerome Charyn likened it to a doomed “Huckleberry Finn.”

In 1981, McCarthy was awarded a MacArthur Fellowship, worth $236,000. Saul Bellow, Shelby Foote, and others had recommended McCarthy to the organization. At this time, McCarthy left his wife. The grant enabled him to travel to the South-West, where he could conduct research for his next novel: Blood Meridian, or the Evening Redness in the West (1985). The book is well known for its violence, with the New York Times declaring it “bloodiest book since the Iliad.” Although initially snubbed by many critics, the book has grown appreciably in stature in literary circles; Harold Bloom called Blood Meridian “the greatest single book since Faulkner’s As I Lay Dying”. In a 2006 poll of authors and publishers conducted by The New York Times Magazine to list the greatest American novels of the previous quarter-century, Blood Meridian placed third, behind only Toni Morrison’s Beloved (1987) and Don DeLillo’s Underworld (1997). Some have even suggested that it is the Great American novel. It was also included on Time magazine’s 2005 list of the 100 best English-language books published since 1923. At the time, he was living in a stone cottage behind an El Paso shopping center, which he described as “barely habitable.”

As of 1991, none of McCarthy’s novels had sold more than 5,000 hardcover copies, and “for most of his career, he did not even have an agent.” He was labelled as the “best unknown novelist in America.”

McCarthy makes sparse use of punctuation, even replacing most commas with “and” to create polysyndetons. The word “and” has been called “the most important word in McCarthy’s lexicon.” He told Oprah Winfrey that he prefers “simple declarative sentences” and that he uses capital letters, periods, an occasional comma, a colon for setting off a list, but never semicolons. He does not use quotation marks for dialogue and believes there is no reason to “blot the page up with weird little marks”. Erik Hage notes that McCarthy’s dialogue also often lacks attribution, but that “Somehow…the reader remains oriented as to who is speaking”. His attitude to punctuation dates to some editing work he did for a professor of English while he was enrolled at the University of Tennessee, when he stripped out much of the punctuation in the book being edited, which pleased the professor. McCarthy also edited fellow Santa Fe Institute Fellow W. Brian Arthur’s influential article “Increasing Returns and the New World of Business”, published in the Harvard Business Review in 1996, removing commas from the text. He has also done copy-editing work for physicists Lawrence M. Krauss and Lisa Randall.

In 2003, while sleeping at an El Paso motel with his son, McCarthy imagined the city in a hundred years: “fires up on the hill and everything being laid to waste.” He wrote two pages covering the idea; four years later in Ireland he would expand the idea into his tenth novel, The Road. It follows a lone father and his young son traveling through a post-apocalyptic America, hunted by cannibals. Many of the discussions between the Father and the Boy were verbatim conversations McCarthy had had with his son. Released in 2006, it won international acclaim and the Pulitzer Prize for Fiction. McCarthy did not accept the prize in person, instead sending Sonny Mehta in his place. A 2009 film adaptation was directed by John Hillcoat, written by Joe Penhall, and starred Viggo Mortensen and Kodi Smit-McPhee. Critics were mostly favorable in their reviews: Roger Ebert found it “powerful but lacks…emotional feeling”, Peter Bradshaw noted “a guarded change of emphasis”, while Dan Jolin found it to be a “faithful adaptation of Cormac McCarthy’s devastating novel”.

In 2003, literary critic Harold Bloom named McCarthy as one of the four major living American novelists, alongside Don DeLillo, Thomas Pynchon, and Philip Roth. His 1994 book The Western Canon had listed Child of God, Suttree, and Blood Meridian among the works of contemporary literature he predicted would endure and become “canonical”. Bloom reserved his highest praise for Blood Meridian, which he called “the greatest single book since Faulkner’s As I Lay Dying”, and though he held less esteem for McCarthy’s other novels he said that “to have written even one book so authentically strong and allusive, and capable of the perpetual reverberation that Blood Meridian possesses more than justifies him. … He has attained genius with that book.”

Also in 2006, McCarthy published the play The Sunset Limited. Critics noted that the play was unorthodox and that it may have had more in common with a novel, hence McCarthy’s subtitle: “a novel in dramatic form.” McCarthy later adapted it into a screenplay for a 2011 HBO film. It was directed and executive produced by Tommy Lee Jones, who also starred opposite Samuel L. Jackson.

In the late 1990s, McCarthy moved to the Tesuque, New Mexico area, north of Santa Fe, with his third wife, Jennifer Winkley, and their son, John. McCarthy and Winkley divorced in 2006.

Oprah Winfrey selected McCarthy’s The Road as the April 2007 entry in her Book Club. As a result, McCarthy agreed to his first television interview, which aired on The Oprah Winfrey Show on June 5, 2007. The interview took place in the library of the Santa Fe Institute. McCarthy told Winfrey that he does not know any writers and much prefers the company of scientists. During the interview, he related several stories illustrating the degree of outright poverty he endured at times during his career as a writer. He also spoke about the experience of fathering a child at an advanced age, and how his son was the inspiration for The Road.

In 2012, McCarthy sold his original screenplay The Counselor to Nick Wechsler, Paula Mae Schwartz, and Steve Schwartz, who had previously produced the film adaptation of McCarthy’s novel The Road. Directed by Ridley Scott, production finished in 2012. It was released on October 25, 2013, to polarized critical reception. Mark Kermode of The Guardian found it “datedly naff”; Peter Travers of the Rolling Stone described it as “a droning meditation on capitalism”; however Manohla Dargis of the New York Times found it “terrifying” and “seductive”.

In 2015, it was announced that McCarthy’s next novel, The Passenger, would be released in 2016. It was described as “full-blown Cormac 3.0—a mathematical [and] analytical novel,” influenced by his time among scientists at the SFI. The novel is also notable as it is his first to feature a female protagonist. As of August 2020, the novel has yet to be released.

In 2016, a hoax spread on Twitter regarding his death, with USA Today even repeating the information. The Los Angeles Times responded to the hoax with the headline, “Cormac McCarthy isn’t dead. He’s too tough to die.”