Vincentio is the Duke of Vienna who temporarily steps away from his public duties. Rather than leave the city, he adopts the disguise of a friar named Lodowick to secretly observe how his citizens behave and how his deputy enforces the laws. He possesses a great deal of power and acts with introspection, preferring to operate behind the scenes to test the honesty of his subjects.

Angelo is a courtier in Vienna with a reputation for extreme moral strictness. Placed in charge of the city during the Duke's absence, he immediately enforces long-ignored laws against sex outside of marriage. He orders the destruction of brothels and condemns offenders to death. His supposedly emotionless disposition is tested when he meets Isabella, leading him to experience forbidden desires.

Isabella is a highly virtuous young woman preparing to dedicate her life to religion as a nun in a strict monastic order. She possesses a talent for reasonable, persuasive speech. When her brother faces execution, she leaves the convent temporarily to plead for his life, throwing her strong moral convictions into direct confrontation with the corrupt legal system.

Lucio is a young gentleman of Vienna who freely associates with both the upper class and the city's sex workers. He serves as a messenger who informs Isabella of her brother's fate and encourages her to plead for his life. Careless with his words, he frequently spreads rumors and openly insults Duke Vincentio, entirely unaware of the ruler's disguise.

Claudio is a young Viennese man condemned to death under the city's newly enforced moral laws. He considers himself practically married to Juliet, having only delayed their formal wedding to secure her dowry. Facing execution, he experiences intense fear of death and uncertainty regarding the afterlife.

Juliet is Claudio's fiancée, currently pregnant with his child. She loves Claudio deeply and views their physical relationship as a mutual act of devotion. She repents for committing the act outside of a legally formalized marriage, recognizing that her pregnancy serves as the physical evidence condemning Claudio.

Escalus is a wise, elderly counselor loyal to Duke Vincentio. He advises Angelo to show mercy and moderation in his rulings, remembering that all humans are capable of making mistakes. Despite his compassionate nature, he remains committed to upholding the law as a stabilizing presence in the courtroom.

Mariana is a local woman who was previously engaged to Angelo. Her marriage contract was broken by Angelo after her brother died in a shipwreck, taking her dowry with him. She lives a quiet, sorrowful life but remains emotionally tied to her former fiancé.

Mistress Overdone operates a brothel in the suburbs of Vienna. She worries about her livelihood as Angelo begins strictly enforcing the laws against sex work and orders the suburban brothels to be torn down.

Pompey works as a bartender and pimp at Mistress Overdone's brothel. He is practical and unrepentant about his illegal profession, eventually adapting to his circumstances by taking a job within the prison to avoid physical punishment.

Elbow is a bumbling, simple-minded city constable who frequently misspeaks and uses words incorrectly. He attempts to uphold the law but often confuses the magistrates with his tangled explanations of crimes.

Froth is a foolish patron of Mistress Overdone's brothel who gets arrested by Elbow. He denies any wrongdoing when questioned by the magistrates.

Friar Thomas is a monk who assists Duke Vincentio by providing him with a disguise and a place to stay while the Duke pretends to have left the city.

Francisca is a nun in the convent Isabella intends to join. She instructs Isabella on the strict rules regarding communication with men.

The Provost is the manager of the Vienna prison. He carries out the orders of the state but demonstrates compassion for his prisoners, particularly Claudio, and is willing to listen to the disguised Duke's instructions.

Abhorson is the official executioner at the Vienna prison. He takes pride in his grim profession, considering it more honest and penitent than the work of a brothel employee.

Barnardine is a long-term prisoner in the Vienna jail. He is a persistent drunkard who stubbornly ignores the moral advice of the friars and bluntly refuses to participate in his own execution.

Friar Peter is a monk who assists Duke Vincentio in coordinating the final stages of his plan, helping to guide Isabella and Mariana in presenting their cases to the public.