Alex is a deeply neurotic, young Jewish man working as the Assistant Commissioner of Human Opportunity in New York City. He feels trapped in a constant struggle between his unrelenting sexual urges and his ethical impulses. Paralyzed by guilt and shame, he unloads his fragmented memories onto his therapist, wrestling with his overbearing upbringing and his persistent sense of alienation as a Jewish man in America.

Alex's mother is a meticulous housekeeper who heavily monitors her son's every movement. She operates as an overbearing force in the Portnoy household, veering rapidly between fierce affection and strange, frightening punishments. Her intense focus on diet, social standing, and behavioral perfection deeply shapes her son's adult neuroses.

Alex's father is a hard-working life insurance salesman who struggles to earn the respect of his clients. He is both physically and emotionally blocked, bottling up his feelings while pressuring his son to achieve the professional success he never could. Despite their differences, he attempts to bond with his son through traditional community activities.

The Monkey is a young gentile woman who becomes a significant romantic presence in Alex's life. Coming from an abusive background and carrying trauma from a previous marriage to a wealthy French industrialist, she is highly sexualized but ultimately vulnerable. She struggles with Alex's constant intellectual demands and hopes to find a stable life with him.

Dr. Spielvogel is a silent, attentive psychoanalyst working with Alex. He serves as the primary sounding board for his patient's extended, nonlinear monologue about childhood, family, and sexual obsessions. His quiet presence drives Alex to constantly attempt to impress him.

Naomi is a strong, physically capable Lieutenant in the Israeli Army. She possesses a firm sense of personal and cultural identity that sharply contrasts with the anxieties of American tourists. When presented with impulsive romantic proposals, she quickly sees through insecurities and fiercely defends her own boundaries.

Hannah is Alex's sister, a steady background presence in the chaotic Portnoy household. Because their parents constantly praise Alex's intellect, he feels an underlying pressure to prove he is smarter than her.

Morty is a young man with strong political convictions who enters the Portnoy family orbit. He possesses manly, left-wing sensibilities that briefly inspire those around him to care about the working class.

Bubbles is a local Italian girl who is involved in early, confusing sexual encounters for the boys in her neighborhood. She is rough, impatient, and openly prejudiced against the Jewish residents of her town.

Arnold is a childhood friend who is left largely unsupervised following his father's death. Though he is wild in his youth and brags openly about his early sexual exploits, he eventually grows up to be a surprisingly traditional, middle-class family man.

The Pumpkin is a gentile college student who brings her boyfriend home for the holidays. Her family's deeply ingrained Christian traditions heavily alienate her guests, highlighting cultural divides.

The Pilgrim is a beautiful gentile woman whose ancestors came to America in the 17th century. Despite her pedigree, wealth, and physical appeal, her minor personal quirks quickly become excuses for her partners to sabotage the relationship.

Uncle Hymie is a family patriarch living in Newark who provides a crowded but safe home for his extended relatives. He is highly protective of his son, going to extreme lengths to preserve his family's cultural standing.

Aunt Clara is an unwell relative who lives in Newark. She is a quiet background figure in the crowded household that temporarily absorbs her extended family.

Heshie is an athletic young man who draws admiration for his physical prowess. He creates tension in his family by falling in love with a gentile girl before going off to serve in the military.