Pollock was born in Cody, Wyoming in 1912, the youngest of five sons. His parents, Stella May McClure and Leroy Pollock, grew up in Tingley, Iowa. His father had been born McCoy but took the surname of his neighbors, who adopted him after his own parents had died within a year of each other. Stella and LeRoy Pollock were Presbyterian; the former, Irish; the latter, Scotch-Irish. LeRoy Pollock was a farmer and later a land surveyor for the government. Jackson grew up in Arizona and Chico, California.
While living in Echo Park, California, he enrolled at Los Angeles' Manual Arts High School, from which he was expelled, after having been expelled another high school in 1928. During his early life, he experienced Native American culture while on surveying trips with his father. In 1930, following his brother Charles Pollock, he moved to New York City where they both studied under Thomas Hart Benton at the Art Students League of New York. Benton's rural American subject matter shaped Pollock's work only fleetingly, but his rhythmic use of paint and his fierce independence were more lasting influences. From 1938 to 1942, Pollock worked for the WPA Federal Art Project.
In attempts to fight his alcoholism, from 1938 through 1941 Pollock underwent Jungian psychotherapy with Dr. Joseph Henderson and later with Dr. Violet Staub de Laszlo in 1941-1942. Dr. Henderson was an eclectic who drew upon the spectrum of psychoanalytic theory, including Freud and Jung. Henderson made the decision to engage him through his art and had Pollock make drawings, which led to the appearance of many Jungian concepts in his paintings. Recently it has been hypothesized that Pollock might have had bipolar disorder.