A gentleman of no particular worth or virtue. He fathers Francisca's child out of wedlock and subsequently makes arrangements to dispose of his offspring. Pressured by Francisca's brother Antonio, he consents to marrying her, without suspecting that the wedding ceremony is set up by his brother-in-law to be a trap to kill him and the disgraced Francisca. He survives this ploy because Antonio's servant Hermio defies his master's orders to poison the chalice that he offers to the couple.
ALMACHILDES
A ridiculous and vain gentleman, he pursues Amoretta without serious intentions. He is used by the Duchess in her plot against her husband, but defies her orders to kill the Duke and thus enables the reconciliation of the noble couple at the end of the play.
AMORETTA
The Duchess's woman, wooed by Almachildes with the aid of charms procured from Hecate. She is instrumental in the arrangements between Almachildes and the Duchess, who tries to get the former to kill her husband. At the end of the play she clears her mistress from the charge of adultery.
ANTONIO
Married to Isabella after having falsely led her to believe that Sebastian, her contracted husband, is dead. Soon after their marriage, his sister Francisca tells him that his wife is deceiving him. Jealous, he sets a trap to catch Isabella and her lover red-handed in his own house. Instead of his adulterous wife and her lover, however, he merely finds and attacks Florida, his own courtesan, and Gaspero, his servant, lured into Isabella's chamber under a pretext by Francisca. Francisca admits that leading Antonio to believe in his wife's infidelity is a ruse to forestall discovery of her own unwanted pregnancy by Aberzanes. By way of punishing his disgraced sister, Antonio sets up a putative wedding ceremony during which he means to poison her and her lover. His ploy fails because his servant Hermio defies his master's orders to poison the chalice that he offers to the couple. Having learnt from Florida about an adulterous assignation between his wife and her servant Celio (Sebastian in disguise) in Fernando's house, the infuriated Antonio meets his end when he falls through a false trap-door into a dungeon.
CELIO
The alias assumed by Sebastian in order to become Isabella's servant and lure her away from her false husband, Antonio, and back into the lawful bond of marriage to which Sebastian is entitled by virtue of a precontract.
DUCHESS
Only superficially a submissive and obedient wife, she loathes the psychological brutality of her husband, the Duke, and seeks revenge. She hires Almachildes to murder her husband, leading him to believe that she will marry him as a reward, without actually intending to do so. Instead, as soon as she thinks that her husband is dead, she tries to seduce the Lord Governor of Ravenna, who also seems to respond to her advances. When he confronts her with the body of her dead husband, the Duchess, by now guilt-ridden, admits to her plan to have him murdered and is sentenced to death. At this moment, the Duke, who had merely pretended to be dead in order to test his wife's virtue, miraculously comes back to life, pardoning her and promising to be a better husband.
FATHER OF THE DUCHESS
A "ghost character." He appears on stage only as a skull that the Duke, is son-in-law, has had made into a chalice.
DUKE
His loathsome brutality is spectacularly expressed by the chalice made of the skull of his wife's father, which the Duke passes around during Antonio and Isabella's nuptials. After his wife, the Duchess, has made arrangements to have him killed, he is mysteriously absent from the play, leading her (and probably also the audience) to believe that her plan was successful. His death, however, is a mere test of his wife's virtue. Confronted with his body, the guilt-ridden Duchess admits that she has murdered her husband and is sentenced to death. At this point the Duke reveals that he is still alive after all, pardoning the Duchess and promising to be a better husband.
FERNANDO
Sebastian's honest and loyal friend who supports his plan to win back Isabella
FIRESTONE
Hecate's mischievous son and aide, whose hypocritical if not malicious comments ridicule his mother's powers.
FLORIDA
Antonio's long-time courtesan. Deeply wounded by his marriage to Isabella, she becomes Sebastian's instrument in his intrigue to win back his contracted wife. When Antonio discovers her in Isabella's chamber with the innocent Gaspero, his servant, she is subjected to her lover's jealous rage but remains faithfully enamoured of him to his death.
FRANCISCA
Antonio's unmarried sister, who has a child by the worthless Aberzanes. Fearing that Isabella, her sister-in-law, might reveal her disgrace to her brother, she tries to damage Isabella's reputation with her husband by leading him to believe that she is unfaithful. This plan fails and Francisca is forced to disclose her own secret to her brother. Antonio then forces her to marry to Aberzanes with the intention of murdering the couple during the wedding ceremony. Francisca and Aberzanes survive, however, when Antonio's servant Hermio defies his master's plan to put poison in the chalice that he offers to the couple.
GASPERO
Antonio's servant, confidant and accessory in his plans to marry Isabella. Francisca suspects him to have informed her sister-in-law about her child by Aberzanes and sets him up in a compromising situation leading his master to believe that he is Isabella's lover and causing the Duke to attack him in a jealous rage.
HECATE
The chief witch. She is a focal point in the play, providing first Sebastian, then Almachildes and finally the Duchess with charms and hints for their schemes. An impressive authority, she nevertheless is a mortal, and her powers are limited. With her concoctions, dances and spells, she reflects the Jacobeans' morbid fascination with the supernatural and allows for elaborate and eerie stage effects.
HERMIO
Antonio's well-meaning servant. He crosses his master's plan to poison Francisca and Aberzanes during their wedding ceremony by not poisoning their chalice.
ISABELLA
Sebastian's wife by precontract. She marries Antonio because he falsely leads her to believe that her husband is dead. Appalled at Francisca's pregnancy, she threatens to inform Antonio about his sister's secret. However, Francisca tries to forestall this disclosure by leading her brother to believe that his wife is unfaithful. Isabella's contracted husband Sebastian in the disguise of Celio becomes her servant and confidant and is reconciled with her after Antonio's death.
LORD GOVENOR OF RAVENNA
Isabella's uncle. He represents law and order. Overseeing the wedding ceremony between his niece and Antonio, he is seduced by the Duchess after she believes her husband to be dead. He pretends to be taken by her advances, but his responses to the Duchess turn out to be a ploy, part of the Duke's test of her virtue.
OLD WOMAN
She only makes one appearance on stage, with Aberzanes' child in arm. Sent off stage to free Aberzanes from this burden by killing the infant, she has the function of accentuating his ruthless irresponsibility.
MALKIN
A cat-like spirit accompanying Hecate.
SEBASTIAN
On returning from the war, Sebastian learns that his wife by precontract has (through the machinations of the false Antonio) bigamously married Antonio. Sebastian vows to gain her back by sowing strife between her and her husband. He uses a charm procured from Hecate as well as the help of Florida, Antonio's long-time courtesan, to separate the couple. Finally, disguised as Celio, he becomes Isabella's confidant, exposing her husband's deception and, having disclosed his true identity after Antonio has died in an accident, is reconciled with her.