James Dean was born to Winton and Mildred Wilson Dean at the "Seven Gables" apartment house, at the intersection of 4th and McClure Streets in Marion, Indiana. Six years after his father had left farming to become a dental technician, James and his family moved to Santa Monica, California. The family spent some years there, and by all accounts young Jimmy was very close to his mother. According to Michael DeAngelis, she was "the only person capable of understanding him." He was enrolled in Brentwood Public School until his mother died of cancer in 1940. Dean's "moodiness and antisocial behavior are consistently attributed to her loss," and even in later years he still attempted to regain his mother's "sense of understanding in all of his relationships with women during his acting career."

Unable to care for his nine year old son, Winton Dean sent young Dean to live with Winton's sister Ortense and her husband Marcus Winslow on a farm in Fairmount, Indiana, where he entered high school and was brought up with a QuakerMethodist pastor, Rev. James DeWeerd. DeWeerd seemed to have had a formative influence upon the teenager, especially upon his future interests in bull fighting, motor racing and the theater. According to Billy J. Harbin, "Dean had an intimate relationship with his pastor... which began in his senior year of high school and 'endured for many years.' " background. 

In high school, Dean's overall performance was mediocre, but he successfully played on the baseball and basketball team and studied forensicsdrama. After graduating from Fairmount High School on May 16, 1949, Dean moved back to California with his beagle, Maxx, to live with his father and stepmother.

He enrolled in Santa Monica College (SMCC), pledged to the Sigma Nu fraternity and majored in pre-law. Dean transferred to UCLA and changed his major to drama, which resulted in estrangement from his father. While at UCLA, he beat out 350 actors to land the role of Malcolm in Macbeth. At that time, he also began acting with James Whitmore's acting workshop. In January 1951, he dropped out of college to pursue a career as an actor.