Boorman first began by working as a drycleaner and Journalist in the late 1950s. He ran the newsrooms at Southern Television in Southampton and Dover before moving into TV documentary filmmaking, eventually becoming the head of the BBC's Bristol-based Documentary Unit in 1962.

Capturing the interest of Producer David Deutsch, he was offered the chance to direct a film aimed at repeating the success of A Hard Day's Night (directed by Richard Lester in 1964): Catch Us If You Can (1965) is about competing pop group Dave Clark Five. While not as successful commercially as Lester's film, it drew good reviews from distinguished critics such as Pauline Kael and Dilys Powell and smoothed Boorman's way into the film industry. Boorman was drawn to Hollywood for the opportunity to make larger-scale cinema and in Point Blank (1967), based on a Richard Stark novel, brought a stranger's vision to the decaying fortress of Alcatraz and the proto-hippy world of west coast America. Lee Marvin gave the then-unknown Director his full support, telling MGM he deferred all his approvals on the project to Boorman.

After Point Blank, Boorman re-teamed with Lee Marvin and Toshiro Mifune for the robinsonade of Hell in the Pacific (1968), which tells a fable story of two representative Soldiers stranded together on an island.

At the beginning of the 1970s, Boorman was planning to film The Lord of the Rings and corresponded about his plans with the author, J. R. R. Tolkien. Ultimately the production proved too costly, though some elements and themes can be seen in Excalibur.

Boorman achieved much greater resonance with Deliverance (US, 1972, adapted from a novel by James Dickey), the ordeal of four urban men, played by Jon Voight, Burt Reynolds, Ronny Cox and Ned Beatty, who encounter danger from an unexpected quarter while whitewater rafting through the Appalachian backwood. This film became Boorman's first true box office success, earning him several award nominations.

A wide variety of films followed. Zardoz (1974), starring Sean Connery, was a post-apocalyptic science fiction piece, set in the 24th century. According to the director's film commentary, the "Zardoz world" was on a collision course with an "effete" eternal society, which it accomplished, and in the story must reconcile with a more natural human nature.

Boorman was selected as Director for Exorcist II: The Heretic (USA, 1977), a move that surprised the industry given his antipathy to the original film. Boorman declared: "Not only did I not want to do the original film, I told the head of Warner Brothers John Calley I'd be happy if he didn't produce the film too." The original script by Broadway Playwright william Goodhart was intellectual and ambitious, based around the metaphysical nature of the battle between good and evil, and specifically the writings of Catholic theologian Pierre Teilhard De Chardin, "I found It extremely compelling. It was based on Chardin's intoxicating Idea that biological evolution was the first step In God's plan, starting with inert rock, and culminating In humankind." Despite Boorman's continued rewriting throughout shooting, the film was rendered incomprehensible. The film, released in June 1977, was a critical and box office disaster. Boorman was denounced by author william Peter Blatty, the author of the original novel The Exorcist, and william Friedkin, Director of the first Exorcist film. Boorman later admitted that his approach to the film was a mistake. The Heretic is often considered not just the worst film of The Exorcist series, but one of the worst films of all time.

Excalibur (UK, 1981), a long-held dream project of Boorman's, is a retelling of the Arthurian legend, based on Le Morte D'Arthur. Boorman cast actors Nicol Williamson and Helen Mirren against their protests, as the two disliked each other intensely, but Boorman felt their mutual antagonism would enhance their characterizations of the characters they were playing. The production was based in the Republic of Ireland, where Boorman had relocated. For the film he employed all of his children as actors and crew and several of Boorman's later films have been 'family business' productions. The film, one of the first to be produced by Orion Films, was a moderate success.

The Emerald Forest (1985) saw Boorman cast his actor son Charley Boorman as an eco-warrior, in a rainforest adventure that included commercially required elements – action and near-nudity – with authentic anthropological detail. Rospo Pallenberg's original screenplay was adapted into a book of the same name by award-winning author Robert Holdstock. Because the film's distributor faced Business troubles that year, the film did not receive a traditional "For Your Consideration" advertising campaign for the 1985 Academy Awards, despite positive critical reviews. Boorman took the initiative to promote the film himself by making VHS copies available for no charge to Academy members at several Los Angeles-area video rental stores. Boorman's idea later became ubiquitous during Hollywood's award season, and by the 2010s, more than a million Oscar screeners were mailed to Academy members each year. However, Emerald Forest itself received no nominations from Boorman's strategy.

Hope and Glory (1987, UK) is his most autobiographical movie to date, a retelling of his childhood in London during The Blitz. Produced by Goldcrest Films, with Hollywood financing the film, it proved a box office hit in the US, receiving numerous Oscar, BAFTA and Golden Globe nominations. However, his 1990 US-produced comedy about a dysfunctional family, Where the Heart Is, was a major flop.

When his friend David Lean died in 1991, Boorman was announced to be taking over direction of Lean's long-planned adaptation of Nostromo, though the production collapsed. Beyond Rangoon (US, 1995) and The Tailor of Panama (US/Ireland, 2000) both explore unique worlds with alien characters stranded and desperate.

Boorman won the Best Director Award at the 1998 Cannes Film Festival for The General, his biopic of Martin Cahill. The film is about a glamorous, yet mysterious, Criminal in Dublin who was killed, apparently by the Provisional Irish Republican Army. Boorman himself had been one of Cahill's burglary victims, having the gold record awarded for the score to Deliverance stolen from his home.

Boorman has been a longtime resident of the Republic of Ireland and lives in Annamoe, County Wicklow, close to the Glendalough twin lakes. He has seven children. His son Charley Boorman has a career as an actor but reached a wider audience when he and actor Ewan McGregor made a televised motorbike trip across Europe, Central Asia, Siberia, Alaska, Canada, and the Midwest US during 2004. His daughter Katrine Boorman (Igrayne in Excalibur) works as an Actress in France. John Boorman's daughter Telsche Boorman wrote the screenplay for Where the Heart Is. She died of ovarian cancer in 1996 at the age of 36. She was married to the Journalist Lionel Rotcage, the son of French singer Régine. John Boorman also has a daughter, Daisy Boorman, who is the twin sister of Charley, and three other children: Lola, Lee and Lily Mae. He was recently divorced.

Released in 2006, his The Tiger's Tail was a thriller set against the tableau of early 21st century capitalism in Ireland. At the same time, Boorman began work on a long-time pet project of his, a fictional account of the life of Roman Emperor Hadrian (entitled Memoirs of Hadrian), written in the form of a letter from a dying Hadrian to his successor. In the meantime, a re-make/re-interpretation of the classic The Wonderful Wizard Of Oz with Boorman at the helm was announced in August 2009.

In 2007 and 2009 he took part in a series of events and discussions as part of the Arts in Marrakech Festival along with his daughter Katrine Boorman including an event with Kim Cattrall called 'Being Directed'.

In November 2012 he was selected as a President of the main competition jury at the 2012 International Film Festival of Marrakech.

In Autumn 2013 Boorman began shooting Queen and Country, the sequel to his 1987 Oscar-nominated Hope and Glory, using locations in Shepperton and Romania. The film was selected to be screened as part of the Directors' Fortnight section of the 2014 Cannes Film Festival.