Educated by governesses, tutors, and nuns, she was expelled from two schools, including New Hall School, Chelmsford, for her rebellious behaviour, until her family sent her to Florence, where she attended Mrs Penrose's Academy of Art. She also, briefly, attended St Mary's convent school in Ascot. In 1927, at the age of ten, she saw her first Surrealist painting in a Left Bank gallery in Paris and later met many Surrealists, including Paul Éluard. Her father opposed her career as an Artist, but her mother encouraged her. She returned to England and was presented at Court, but according to her, she brought a copy of Aldous Huxley's Eyeless in Gaza (1936) to read instead. In 1935, she attended the Chelsea School of Art in London for one year, and with the help of her father's friend Serge Chermayeff, she was able to transfer to Ozenfant Academy in London (1935–38).

Carrington's art often depicts horses, as in her Self-Portrait (Inn of the Dawn Horse) and the painting The Horses of Lord Candlestick. Her fascination with drawing horses began in her childhood. Horses also appear in her writings. In her first published short story, "The House of Fear", Carrington portrays a horse in the role of a psychic guide to a young heroine. In 1935, Carrington's first essay, "Jezzamathatics or Introduction to the Wonderful Process of Painting", was published before her story "The Seventh Horse". Carrington often used codes of words to dictate interpretation in her artwork. "Candlestick" is a code that she commonly used to represent her family, and the word "lord" for her father.

In 1936, Leonora saw the work of the German surrealist Max Ernst at the International Surrealist Exhibition in London and was attracted to the Surrealist Artist before she even met him. In 1937, Carrington met Ernst at a party held in London. The artists bonded and returned together to Paris, where Ernst promptly separated from his wife. In 1938, leaving Paris, they settled in Saint Martin d'Ardèche in southern France. The new couple collaborated and supported each other's artistic development. The two artists created sculptures of guardian animals (Ernst created his birds and Carrington created a plaster horse head) to decorate their home in Saint Martin d'Ardèche. In 1939, Carrington painted a portrait of Max Ernst, as a tribute to their relationship. The portrait was her first Surrealist work, and it was called The Inn of the Dawn Horse. It is now in the Metropolitan Museum of Art. The person in the painting is a cross between a male and a female, who is seated in a room with a rocking horse on the wall.

In Self-Portrait (1938), Carrington offers her own interpretation of female sexuality by looking toward her own sexual reality rather than theorizing on the subject, as was custom by other Surrealists in the movement. Carrington’s move away from the characterization of female sexuality subverted the traditional male role of the Surrealist movement. Self-Portrait (1938) also offers insight into Carrington’s interest in the ‘alchemical transformation of matter and her response to the Surrealist cult of Desire as a source of creative inspiration.’ The hyena depicted in Self-Portrait (1938) joins both male and female into a whole, metaphoric of the worlds of the night and the dream. The symbol of the hyena is present in many of Carrington's later works, and it was even used to depict Carrington in Max Ernst's work "La Debutante" in his book The Oval Lady.

After Ernst's arrest, Carrington was devastated and fled to Spain. Paralyzing anxiety and growing delusions culminated in a final breakdown at the British Embassy in Madrid. Her parents intervened and had her hospitalised. She was given "convulsive therapy" and was treated with the drugs cardiazol, a powerful anxiolytic drug (eventually banned by some authorities, including the US Food and Drug Administration (FDA)), and Luminal, a barbiturate. After being released into the care of a nurse who took her to Lisbon, Carrington ran away and sought refuge in the Mexican Embassy. Meanwhile, Ernst had married Peggy Guggenheim in New York in 1941. That marriage ended a few years later. Ernst and Carrington never resumed their relationship.

Following the escape to Lisbon, Carrington arranged passage out of Europe with Renato Leduc, a Mexican Ambassador. Leduc was a friend of Pablo Picasso, and agreed to a marriage of convenience with Carrington so that she would be accorded the immunity given to a diplomat's wife. Leduc spirited Carrington away to Mexico, which she grew to love and where she lived, on and off, for the rest of her life. The pair divorced in 1943. Events from this period continued to inform her work.

The first important exhibition of her work appeared in 1947, at the Pierre Matisse Gallery in New York City. Carrington was invited to show her work in an international exhibition of Surrealism, where she was the only female English professional Painter. She became a Celebrity almost overnight. In Mexico, she authored and successfully published several books.

After spending part of the 1960s in New York City, Carrington lived and worked in Mexico once again. While in Mexico, she was asked, in 1963, to create a mural which she named El Mundo Magico de los Mayas, and which was influenced by folk stories from the region. The mural is now located in the Museo Nacional de Antropología in Mexico City.

Surrealismo y Arte Fantástico en México, Galeria Universitaria, Aristos, Mexico 1965: Galería Antonio Souza, Mexico City, Mexico (solo) Instituto Cultural Anglo-Mexicano, Mexico (solo) Galería Clardecor, Mexico City, Mexico (solo)

Carrington designed Mujeres conciencia (1973), a poster, for the Women's Liberation movement in Mexico, depicting a ‘new eve’. Carrington, personally and primarily focused on psychic freedom, understood that such freedom could not be achieved until political freedom is also accomplished. Through these beliefs, Carrington understood that “greater cooperation and sharing of knowledge between politically active women in Mexico and North America” was important for emancipation. Carrington’s political commitment led to her winning the Lifetime Achievement Award at the Women’s Caucus for Art convention in New York in 1986.

In 2005, Christie's auctioned Carrington's Juggler (El Juglar), and the realised price was US$713,000, setting a new record for the highest price paid at auction for a living surrealist Painter. Carrington painted portraits of the telenovela actor Enrique Álvarez Félix, son of Actress María Félix, a friend of Carrington's first husband.

She later married Emerico Weisz (nickname "Chiki"), born in Hungary 1911, a Photographer and the darkroom manager for Robert Capa during the Spanish Civil War. They had two sons: Gabriel, an intellectual and a poet, and Pablo, a Doctor and Surrealist Artist. Chiki Weisz died January 17, 2007, at home. He was 97 years old.

The first major exhibition of her work in UK for twenty years took place at Chichester's Pallant House Gallery, West Sussex, from 17 June to 12 September 2010, as part of a season of major international exhibitions called Surreal Friends that celebrated women's role in the Surrealist movement. Her work was exhibited alongside pieces by her close friends, the Spanish Painter Remedios Varo (1908–1963) and the Hungarian Photographer Kati Horna (1912–2000).

Leonora Carrington died on 25 May 2011, aged 94, in a hospital in Mexico City, as a result of complications arising from pneumonia.

In 2013, Carrington was the subject of a major retrospective at the Irish Museum of Modern Art, Dublin. Titled The Celtic Surrealist, it was curated by Sean Kissane and examined Carrington's Irish background to Illuminate many cultural, political and mythological themes present in her work.

In 2015, Carrington was honoured through a Google Doodle commemorating her 98th birthday. The Doodle was based on her painting, How Doth the Little Crocodile, drawn in surrealist style. The painting was inspired by a poem in Lewis Carroll's Alice's Adventures in Wonderland, and this painting was eventually turned into Cocodrilo located on Paseo de la Reforma.

Carrington stated that: "I painted for myself...I never believed anyone would exhibit or buy my work." She was not interested in the writings of Sigmund Freud, as were other Surrealists in the movement. She instead focused on magical realism and alchemy and used autobiographical detail and symbolism as the subjects of her paintings. Carrington was interested in presenting female sexuality as she experienced it, rather than as that of male surrealists’ characterization of female sexuality. Carrington’s work of the 1940s is focused on the underlying theme of women’s role in the creative process.