Gladys Nilsson was born in Chicago, USA, to Swedish parents in 1940. She trained at the School of the Art Institute of Chicago where she also met her current husband Jim Nutt. Together with Art Green, Suellen Rocca, Jim Falconer, and Karl Wirsum, they formed the artist group "Hairy Who?" in 1965 which was active from 1966 to 1969 and is also known as "the Chicago Imagists". The group was a product of its time, in an America of student uprisings, reactions to the Vietnam War, political assassinations and consumerism. "Hairy Who?" were recognized in Chicago and exhibited throughout the United States.

Gladys Nilsson's primary medium is watercolour, and her work touches on surrealism, pop art, cartooning and fantasy. The human figure is her subject, but it is manipulated, enlarged, doubled and dissected to her liking. The motifs are taken from everyday observations that examine sexuality and gender with a large dose of humor. In 1973, Gladys Nilsson became the first of the "Hairy Who?" members to exhibit at the Whitney Museum of American Art in New York and also one of the first women to exhibit there.

Since Nilsson's first exhibition in 1966, she has had over 50 solo exhibitions, she has exhibited at numerous institutions worldwide and her work is included in prominent collections.