The play is written for eight actors, each of whom plays two or more roles. Kushner's doubling, as indicated in the published script, requires several of the actors to play the opposite sex.
There are nine main characters:
Prior Walter – A gay man with AIDS. Throughout the play, he experiences various heavenly visions. When the play begins, he is dating Louis Ironson. His best friend is a nurse named Belize.
Louis Ironson – Prior's boyfriend. Unable to deal with Prior's disease, he ultimately abandons him. He meets Joe Pitt and later begins a relationship with him.
Harper Pitt – An agoraphobic Mormon housewife with incessant Valium-induced hallucinations. After a revelation from Prior (whom she meets when his heavenly vision and her hallucination cross paths), she discovers that her husband is gay and struggles with it, considering it a betrayal of her marriage.
Joe Pitt – Harper's husband and a deeply closeted gay Mormon, clerk at the U.S. Court of Appeals, Second Circuit, and friend of Roy Cohn. Joe eventually abandons his wife for a relationship with Louis. Throughout the play, he struggles with his sexual identity.
Roy Cohn – A closeted gay lawyer, based on real life Roy Cohn. Just as in history, it is eventually revealed that he has contracted HIV and the disease has progressed to AIDS, which he insists is liver cancer to preserve his reputation.
Ethel Rosenberg – The ghost of a woman executed for being a Communist spy, based on the real life Ethel Rosenberg. She visits Roy, whom she blames for her conviction and execution. She is traditionally played by the same actress as Hannah Pitt.
Hannah Pitt – Joe's mother. She moves to New York after her son drunkenly comes out to her on the phone. She arrives to find that Joe has abandoned his wife.
Belize – A former drag queen, he is Prior's ex-boyfriend and best friend. He later becomes Roy Cohn's nurse.
The Voice/Angel – A messenger from Heaven who visits Prior and tells him he's a prophet.
There are also a series of supporting and minor characters played by the core eight actors:
Rabbi Isidor Chemelwitz – An elderly orthodox Rabbi. He performs the funeral service for Louis' grandmother in Act one of Millennium Approaches and gives him advice on his situation with Prior. Played by the same actress as Hannah.
Mr. Lies – One of Harper's imaginary friends. A smooth talking agent for the International Order of Travel Agents. Played by the same actor as Belize.
Emily – A smart-mouthed nurse who attends to Prior. Played by the same actress as The Angel.
Henry – Roy Cohn's doctor, who diagnoses him with AIDS. Played by the same actress as Hannah.
Martin Heller – A publicity agent to the Reagan Administration's Justice Department and Roy's toady. Played by the same actress as Harper.
Prior 1 and Prior 2 – The ghosts of two of Prior Walter's ancestors. Prior 1 was a gloomy Yorkshire farmer from the thirteenth century while Prior 2 was a seventeenth century British aristocrat. They both arrive to herald The Angel's arrival. Played by the same actors as Joe and Roy, respectively.
The Man in The Park – A gay prostitute Louis has sex with in Central Park. Played by the same actor as Prior.
Sister Ella Chapter – Hannah's realtor friend who helps her sell her house. Played by the same actress as The Angel.
The Woman in the South Bronx – A crazed homeless woman Hannah encounters when she arrives in New York. Played by the same Actress as The Angel.
The Eskimo – An imaginary friend in Harper's Antarctic hallucination. Played by the same actor as Joe.
Aleksii Antedilluvianovich Prelapsarianov – "The World's Oldest Living Bolshevik", whose speech in the opening of Perestroika sets up the theme of whether the world should continue to move forward. Played by the same actress as Hannah.
Mormon Family – A mannequin family in the Diorama Room of the Mormon's Visitor Center where Hannah and Harper volunteer. The Father resembles Joe, and later becomes him in Harper's delusions. The Mother comes to life in Harper's imagination and speaks to her. She is played by the same actress as The Angel. The two sons, Caleb and Orr, are voiced offstage by the same actors as Belize and The Angel respectively.
The Continental Principalities – The Angel Council Prior confronts in Heaven. They are in charge of both Heaven and Earth after God's desertion. They are the Angels of Europa (played by the actor playing Joe), Africanii (played by the actor playing Harper), Oceania (played by the actor playing Belize), Asiatica (played by the actor playing Hannah), Australia (played by the actor playing Louis), and Antarctica (played by the actor playing Roy).
Sarah Ironson – Louis' dead grandmother whom Prior meets in Heaven playing cards with the Rabbi. Played by the same actor as Louis.