After the war, filled with new ideas, Ernst, Jean Arp and social activist Alfred Grünwald formed the Dada group. In 1918 he married the art historian Luise Straus — a stormy relationship that would not last. The couple had a son who was born in 1920, the artist Jimmy Ernst. In 1919 Ernst visited Paul Klee and created paintings, block prints and collages, and experimented with mixed media.
In 1922, he joined fellow Dadaists André Breton, Gala, Tristan Tzara, and Paul Éluard at the artistic community of Montparnasse. Constantly experimenting, in 1925 he invented a graphic art technique called frottage, which uses pencil rubbings of objects as a source of images. He also created another technique called 'grattage' in which paint is scraped across canvas to reveal the imprints of the objects placed beneath.
The next year he collaborated with Joan Miró on designs for Sergei Diaghilev. With Miró's help, Ernst pioneered grattage in which he troweled pigment from his canvases. He also explored with the technique of decalcomania which involves pressing paint between two surfaces.
Ernst developed a fascination with birds that was prevalent in his work. His alter ego in paintings, which he called Loplop, was a bird. He suggested this alter-ego was an extension of himself stemming from an early confusion of birds and humans. He said that one night when he was young he woke up and found that his beloved bird had died, and a few minutes later his father announced that his sister was born.
In 1927 he married Marie-Berthe Aurenche. In 1930, he appeared in the film L'Âge d'or, directed by self-identifying Surrealist Luis Buñuel. Ernst began to make sculpture in 1934, and spent time with Alberto Giacometti. In 1938, the American heiress and artistic patron Peggy Guggenheim acquired a number of Max Ernst's works which she displayed in her new museum in London.
In 1938 he was interned in Camp des Milles, near Aix-en-Provence, along with fellow surrealist, Hans Bellmer, who had recently emigrated to Paris on the outbreak of World War II. Thanks to the intercession of Paul Éluard, and other friends he was discharged a few weeks later. Soon after the Nazi occupation of France, he was arrested again, this time by the Gestapo, but managed to escape and flee to America with the help of Peggy Guggenheim. They arrived in the United States in 1941 and were married the following year. Along with other artists and friends (Marcel Duchamp and Marc Chagall) who had fled from the war and lived in New York City, Ernst helped inspire the development of Abstract Expressionism.
His marriage to Guggenheim did not last, and in Beverly Hills, California in October 1946, in a double ceremony with Man Ray and Juliet P. Browner, he married Dorothea Tanning. The couple first made their home in Sedona, Arizona. In 1948, Ernst wrote the treatise "Beyond Painting". As a result of the publicity, he began to achieve financial success.
In 1953 he and Tanning moved to a small town in the south of France where he continued to work. Ernst died on 1 April 1976, 1 day before his birthday, in Paris.