Personal relationships 

Screenwriter William Bast was one of Dean's closest friends, a fact acknowledged by Dean's family. According to Dean's first biographer (1956), Bast was his roommate at UCLAand later in New York, and knew Dean throughout the last five years of his life. Fifty years after Dean's death, he stated that their friendship had included some sexual intimacy.

Early in Dean's career, after Dean signed his contract with Warner Brothers, the studio's public relations department began generating stories about Dean's liaisons with a variety of young actresses who were mostly drawn from the clientele of Dean's Hollywood agent, Dick Clayton. Studio press releases also grouped "Dean together with two other actors, Rock Hudson and Tab Hunter, identifying each of the men as an 'eligible bachelor' who has not yet found the time to commit to a single woman: 'They say their film rehearsals are in conflict with their marriage rehearsals.'"

Dean's best-remembered relationship was with young Italian actress Pier Angeli, whom he met while Angeli was shooting The Silver Chalice on an adjoining Warner lot, and with whom he exchanged items of jewelry as love tokens. Angeli's mother was reported to have disapproved of the relationship because Dean was not Roman Catholic.

In his autobiography, East of Eden director Elia Kazan, while dismissing the notion that Dean could possibly have had any success with women, paradoxically alluded to Dean and Angeli's "romance", claiming that he had heard them loudly making love in Dean's dressing room. For a very short time the story of a Dean-Angeli love affair was even promoted by Dean himself, who fed it to various gossip columnists and to his co-star, Julie Harris, who in interviews has reported that Dean told her about being madly in love with Angeli.

However, in early October 1954, Angeli had unexpectedly announced her engagement to Italian-American singer Vic Damone, to Dean's expressed irritation. Angeli married Damone the following month, and gossip columnists reported that Dean, or someone dressed like him, watched the wedding from across the road on a motorcycle. However, when Bast questioned him about the reports, Dean denied that he would have done anything so "dumb", and Bast, like Paul Alexander, believes the relationship was a mere publicity stunt. Pier Angeli only talked once about the relationship in her later life in an interview, giving vivid descriptions of romantic meetings at the beach. Dean biographer John Howlett said these read like wishful fantasies, as Bast claims them to be.

Actress Liz Sheridan claims that she and Dean had a short affair in New York. However, again Bast is skeptical whether this was a true love affair and says Dean and Sheridan did not spend much time together. He has also dated actress Ursula Andress.

Dean avoided the draft by registering as a homosexual, then classified by the US government as a mental disorder. When questioned about his orientation, he is reported to have said, "No, I am not a homosexual. But, I'm also not going to go through life with one hand tied behind my back."