He was born Endre Friedmann to the Jewish family of Júlia (née Berkovits) and Dezső Friedmann in Budapest, Austria-Hungary October 22, 1913. His mother, Julianna Henrietta Berkovits was a native of Nagykapos (now Veľké Kapušany, Slovakia) and Dezső Friedmann came from the Transylvanian village of Csucsa (now Ciucea, Romania). At the age of 18, he was accused of alleged communist sympathies and was forced to flee Hungary.

The British magazine Picture Post ran his photos from Spain in the 1930s accompanied by a portrait of Capa, in profile, with the simple description: "He is a passionate democrat, and he lives to take photographs."

As a young boy, Capa was drawn to the Munkakör (Employment Circle), a group of socialist and avant-garde artists, Photographers, and intellectuals centered around Budapest. He participated in the demonstrations against the Miklós Horthy regime. In 1931, just before his first photo was published, Capa was arrested by the Hungarian secret police, beaten, and jailed for his radical political activity. A police official's wife—who happened to know his family—won Capa's release on the condition that he would leave Hungary immediately.

Capa's first published photograph was of Leon Trotsky making a speech in Copenhagen on "The Meaning of the Russian Revolution" in 1932.

Capa originally wanted to be a writer; however, he found work in photography in Berlin and grew to love the art. In 1933, he moved from Germany to Paris because of the rise of Nazism and its persecution of Jews, but found it difficult to find work as a freelance Journalist. He changed his name to the more American-sounding name, Robert Capa, to avoid religious discrimination then Common in France, which allowed him to find work more easily.

In 1934 "André Friedman", as he still called himself then, met Gerda Pohorylle, a German Jewish refugee. The couple lived in Paris where André taught Gerda photography. Together they created the name and image of "Robert Capa" as a famous American Photographer, and at the beginning of the war both Photographers published their work under the pseudonym of Robert Capa. Gerda took the name Gerda Taro and became successful in her own right. She travelled with Capa to Spain in 1936 intending to document the Spanish Civil War. In July 1937, Capa traveled briefly to Paris while Gerda remained in Madrid. She was killed near Brunete during a battle. Capa, who was reportedly engaged to her, was deeply shocked and never married.

From 1936 to 1939, Capa worked in Spain, photographing the Spanish Civil War, along with Gerda Taro, his companion and professional photography partner, and David Seymour. Taro died when the motor vehicle on which she was travelling (apparently standing on the footboard) collided with an out-of-control tank. She had been returning from a photographic assignment covering the Battle of Brunete.

In 1938, he traveled to the Chinese city of Hankou, now within Wuhan, to document the resistance to the Japanese invasion. He sent his images to Life magazine, which published some of them in its May 23, 1938 issue.

Capa accompanied then Journalist and author Ernest Hemingway to photograph the war, which Hemingway would later describe in his novel, For Whom the Bell Tolls (1940). Life magazine published an article about Hemingway and his time in Spain, along with numerous photos by Capa.

In February 1943 Capa met Elaine Justin, then married to the actor John Justin. They fell in love and the relationship lasted until the end of the war. Capa spent most of his time in the frontline. Capa called the redheaded Elaine "Pinky," and wrote about her in his war memoir, Slightly Out of Focus. In 1945, Elaine Justin broke up with Capa; she later married Chuck Romine.

The eleven prints that survived were included in Life magazine's issue on June 19, 1944. The article described how Capa got some of his shots:

Some months later Capa became the lover of the Actress Ingrid Bergman, who was touring in Europe to entertain American Soldiers. In December 1945, Capa followed her to Hollywood, where he worked for American International Pictures for a short time. The relationship ended in the summer of 1946 when Capa traveled to Turkey.

In 1947, Capa founded the cooperative venture Magnum Photos in Paris with Henri Cartier-Bresson, william Vandivert, David Seymour, and George Rodger. It was a cooperative agency to manage work for and by freelance Photographers, and developed a reputation for the excellence of its photo-journalists. In 1952, he became the President.

Capa fled political repression in Hungary when he was a teenager, moving to Berlin, where he enrolled in college. He witnessed the rise of Hitler, which led him to move to Paris, where he met and began to work with Gerta Pohorylle. Together they worked under the alias Robert Capa and became photojournalists. Though she contributed to much of the early work, she quickly created her own alias 'Gerda Taro' and they began to publish their work separately. He subsequently covered five wars: the Spanish Civil War, the Second Sino-Japanese War, World War II across Europe, the 1948 Arab–Israeli War, and the First Indochina War, with his photos published in major magazines and newspapers.

In the early 1950s, Capa traveled to Japan for an exhibition associated with Magnum Photos. While there, Life magazine asked him to go on assignment to Southeast Asia, where the French had been fighting for eight years in the First Indochina War. Capa was killed when he stepped on a land mine. He was 40 years old.

He is credited with coining the term Generation X. He used it as a title for a photo-essay about the young people reaching adulthood immediately after the Second World War. It was published in 1953 in Picture Post (UK) and Holiday (USA). Capa said, "We named this unknown generation, The Generation X, and even in our first enthusiasm we realised that we had something far bigger than our talents and pockets could cope with."

His younger brother, Cornell Capa, also a Photographer, worked to preserve and promote Robert's legacy as well as develop his own identity and style. He founded the International Fund for Concerned Photography in 1966. To give this collection a permanent home, he founded the International Center of Photography in New York City in 1974. This was one of the foremost and most extensive conservation efforts on photography to be developed. Indeed, Capa and his brother believed strongly in the importance of photography and its preservation, much like film would later be perceived and duly treated in a similar way. The Overseas Press Club created the Robert Capa Gold Medal in the photographer's honor.

In December 2007, three boxes filled with rolls of film, containing 4,500 35mm negatives of the Spanish Civil War by Capa, Taro, and Chim (David Seymour), —which had been considered lost since 1939, were discovered in Mexico. In 2011, Trisha Ziff directed a film about those images, entitled The Mexican Suitcase.

In 1947, for his work recording World War II in pictures, U.S. President Dwight D. Eisenhower awarded Capa the Medal of Freedom Citation The International Center of Photography organized a travelling exhibition titled This Is War: Robert Capa at Work, which displayed Capa's innovations as a photojournalist in the 1930s and 1940s. It includes vintage prints, contact sheets, caption sheets, handwritten observations, personal letters and original magazine layouts from the Spanish Civil War, the Second Sino-Japanese War and World War II. The exhibition appeared at the Barbican Art Gallery, the International Center of Photography of Milan, and the Museu Nacional d'Art de Catalunya in the fall of 2009, before moving to the Nederlands Fotomuseum from October 10, 2009 until January 10, 2010.

The government of Hungary issued a postage stamp in Capa's honor in 2013. That same year it issued a 5,000 forint ($20) gold coin, also in his honor, showing an engraving of Capa.

The Boston Review has described Capa as "a leftist, and a democrat—he was passionately pro-Loyalist and passionately anti-fascist ..." During the Spanish Civil War, Capa travelled with and photographed the Workers' Party of Marxist Unification (POUM), which resulted in his best-known photograph.