Johns is regarded as one of America’s greatest contemporary artists. His best-known work is Flag (1954–1955), inspired by a dream he had of the American flag.

Johns’s work is often classified as Neo-Dada rather than Pop Art, although his materials frequently include images and objects from popular culture. Nevertheless, many introductions to Pop Art include his work because of his practice of giving new meaning to a familiar image or object.

Johns’s early works were inspired by simple objects: his paintings directly depicted such things as the American flag, maps, targets, letters, and numbers. His work is best known for its refined treatment of the painted surface. In some works, he used encaustic, a very old technique for making paint whose principal characteristic is the use of liquid wax, as well as other media including stucco and plaster. Johns’s artistic ideas gave his work a range of avant-garde meanings, much like the work of the Dada artist Duchamp, who occupied an important place in his artistic thinking. Johns also produced prints on a considerable scale, with artistic concepts similar to those in his paintings.