From 1942 to 1946, Klein studied at the École Nationale de la Marine Marchande and the École Nationale des Langues Orientales. At this time, he became friends with Arman (Armand Fernandez) and Claude Pascal and started to paint. At the age of nineteen, Klein and his friends lay on a beach in the south of France, and divided the world between themselves; Arman chose the earth, Pascal, words, while Klein chose the ethereal space surrounding the planet, which he then proceeded to sign:

Between 1947 and 1948, Klein conceived his Monotone Symphony (1949, formally Monotone Silence Symphony) that consisted of a single 20-minute sustained chord followed by a 20-minute silence.

In early 1948, Klein was exposed to Max Heindel’s 1909 text The Rosicrucian Cosmo-Conception and pursued a membership with an American society dedicated to Rosicrucianism.

Although Klein had painted monochromes as early as 1949, and held the first private exhibition of this work in 1950, his first public showing was the publication of the artist’s book Yves Peintures in November 1954. Parodying a traditional catalogue raisonné, the book featured a series of intense monochromes linked to various cities he had lived in during the previous years. Yves Peintures anticipated his first two shows of oil paintings, at the Club des Solitaires, Paris, October 1955 and Yves: Proposition monochromes at Gallery Colette Allendy, February 1956. Public responses to these shows, which displayed orange, yellow, red, pink and blue monochromes, deeply disappointed Klein, as people went from painting to painting, linking them together as a sort of mosaic.

While attending the École Nationale des Langues Orientales Klein began practicing judo. During the years 1948 to 1952, he traveled to Italy, Great Britain, Spain, and Japan. He traveled to Japan in 1953 where he became, at the age of 25, a master at judo receiving the rank of yodan (4th dan/degree black-belt) from the Kodokan, becoming the first European to rise to that rank. Later that year, he became the technical director of the Spanish judo team. In 1954 Klein wrote a book on judo called Les Fondements du judo. The same year, he settled permanently in Paris and began in earnest to establish himself in the art world.

The show was a critical and commercial success, traveling to Paris, Düsseldorf and London. The Parisian exhibition, at the Iris Clert Gallery in May 1957, became a seminal happening. To mark the opening, 1001 blue balloons were released and blue postcards were sent out using IKB stamps that Klein had bribed the postal service to accept as legitimate. Concurrently, an exhibition of tubs of blue pigment and fire paintings was held at Galerie Collette Allendy.

In Blue Obelisk, a project that he had failed to realise in 1958, but that finally happened in 1983, he appropriated the Place de la Concorde by shining blue spotlights onto the central obelisk.

Later in the year, he was invited to decorate the Gelsenkirchen Opera House, Germany, with a series of vast blue murals, the largest of which were 20 metres by 7 metres. The Opera House was inaugurated in December 1959. Klein celebrated the commission by travelling to Cascia, Italy, to place an ex-voto offering at the Saint Rita Monastery. “May all that emerges from me be beautiful,” he prayed. The offering took the form of a small transparent plastic box containing three compartments; one filled with IKB pigment, one filled with pink pigment, and one with gold leaf inside. The container was only rediscovered in 1980.

Sometimes the creation of these paintings was turned into a kind of performance art—an event in 1960, for example, had an audience dressed in formal evening wear watching the models go about their task while an instrumental ensemble played Klein’s 1949 The Monotone Symphony.

The art critic Pierre Restany, who spoke of how his first meeting with Klein had been fundamental to them both, went on to found the Nouveau Réalisme group with Klein in Klein’s studio/apartment on 27 October 1960. Founding members were Arman, Francois Dufrêne, Raymond Hains, Yves Klein, Martial Raysse, Daniel Spoerri, Jean Tinguely, and Jacques Villeglé, with Niki de Saint Phalle, Christo and Gérard Deschamps joining later. Normally seen as a French version of Pop Art, the aim of the group was stated as ‘Nouveau Réalisme—new ways of perceiving the real’ [Nouveau Réalisme nouvelles approches perceptives du réel].

A sort of parody of Klein’s Anthropometry performance is featured in the film Wise Guys (original title: Les Godelureaux) directed by Claude Chabrol released in 1961.

He moved on to exhibit at the Dwan Gallery, Los Angeles, and traveled extensively in the Western U.S., visiting Death Valley in the Mojave Desert. In 1962, he married Rotraut Uecker, sister of German artist Günther Uecker.

He suffered a heart attack while watching the film Mondo cane (in which he is featured) at the Cannes Film Festival on 11 May 1962. Two more heart attacks followed, the second of which killed him on 6 June 1962. His son, Yves Amu Klein [fr], was born on 6 August in Nice. Yves Amu studied architecture, design, cybernetics theory of systems, and fine arts sculpture. He went on to create robotized sculptures. Rotraut Klein married the photographer and designer Daniel Moquay, and has homes in Paris; Phoenix, Arizona; and Sydney, Australia.

Thomas McEvilley, in an essay submitted to Artforum in 1982, classified Klein as an early, though enigmatic, postmodernist artist.

Alongside works by Andy Warhol and Willem de Kooning, Klein’s painting RE 46 (1960) was among the top-five sellers at Christie’s Post-War and Contemporary Art sale in May 2006. His monochromatic blue sponge painting sold for $4,720,000. Previously, his painting RE I (1958) had sold for $6,716,000 at Christie’s New York in November 2000. In 2008, MG 9 (1962), a monochromatic gold painting, sold for $21,000,000 at Christie’s. FC1 (Fire Color 1) (1962), a nearly 10-foot-long panel created with a blowtorch, water and two models, sold for $36.4 million at Christie’s in 2012.

In 2013, Klein’s Sculpture Éponge Bleue Sans Titre, SE 168, a 1959 sculpture made with natural sea sponges drenched in blue pigment fetched $22 million, the highest price paid for a sculpture by the artist.

In 2018, the podcast This is Love released an episode, “Blue,” about Klein and his work.