Jared Leto plays the part of Harry Goldfarb, a small-time heroin addict and dealer who dreams of a better future. Harry is in a downward spiral because of his heroin addiction, and he eventually ends up in prison. He even has to have his arm cut off because of an infection caused by his drug addiction. Leto lived on the streets of New York to prepare himself for the role of Harry, and when filming finished, he shaved his head and lived in a monastery in Portugal for several months to recover. His other movie credits include "Fight Club," "American Psycho," "Alexander" and "Panic Room."
Jennifer Connolly plays Harry's girlfriend Marion Silver. She also dreams of a better future, but when drug addiction takes a hold of her, she resorts to sleeping with her psychologist to get money for her and Harry to buy drugs that they can sell. As her addiction gets worse and her relationship with Harry disintegrates, she begins prostituting herself and takes part in a live sex show in order to fund her habit. Connolly received critical acclaim for the courage she needed to portray the mental and physical degradation of Marion. Marion's fall into drug addiction is perhaps the most disturbing, as by the end of the movie she has come to enjoy her predicament. Other movies Connolly has starred in include "A Beautiful Mind," "Blood Diamond" and "He's Just Not That Into You."
Ellen Burstyn plays Harry's mother Sara Goldfarb. Sara is selected to appear on a TV show, and she starts taking diet pills to lose weight so she can fit into her favorite dress. The pills contain amphetamines, and she becomes addicted to them. As she increases her usage, she starts experiencing hallucinations. As the hallucinations get worse, Sara goes crazy and ends up in a mental institution where she receives electroshock therapy. Burstyn received critical acclaim and a Best Actress nomination for her portrayal of Sara. She also received several critics' awards for effectively portraying such a disturbed character. Other well-known movies Burstyn has acted in include "The Exorcist," "How To Make An American Quilt" and the 2006 remake of "The Wicker Man."
Marlon Wayans plays the part of Tyrone C. Love in the movie. He is Harry's best friend, and the pair of them sell heroin to try and make money. When Tyrone ends up in jail, Harry has to put up bail money for him, and as the pair descend into heroin addiction and run out of cash in New York, they decide to head to Florida to make a drug deal. The pair are arrested and sent to jail, where Tyrone is subjected to racial abuse from one of the prison guards. Wayans, who is best known as a comedy actor, starred in the movie "Dungeons and Dragons," where he filmed all of his scenes over the course of four days before the filming for "Requiem for a Dream" began. He received critical acclaim for the dramatic role of Tyrone. Other movies Wayans has starred in include "Scary Movie" and "Scary Movie 2" and "GI Joe: The Rise of Cobra."