Flavin's first works were drawings and paintings that reflected the influence of Abstract Expressionism. In 1959, he began to make assemblages and mixed media collages that included found objects from the streets, especially crushed cans.

In the summer of 1961, while working as a guard at the American Museum of Natural History in New York, Flavin started to make sketches for sculptures that incorporated electric lights. The first works to incorporate electric light were his "Icons" series: eight colored shallow, boxlike square constructions made from various materials such as wood, Formica, or Masonite. Constructed by the artist and his then-wife Sonja, the Icons had fluorescent tubes with incandescent and fluorescent bulbs attached to their sides, and sometimes beveled edges. One of these icons was dedicated to Flavin's twin brother David, who died of polio in 1962.