John Dowell: The narrator, husband to Florence. Dowell is an American Quaker, either a gullible and passionless man who cannot read the emotions of the people around him or a master manipulator who plays the victim.
Florence Dowell: John Dowell’s wife and a scheming, manipulative, unfaithful woman who uses Dowell for his money while pursuing her affairs on the side. She fakes a heart ailment to get what she wants out of her husband and has a lengthy affair with Edward Ashburnham.
Edward Ashburnham: Friend of the Dowells and husband of Leonora. Ashburnham is a hopeless romantic who keeps falling in love with the women he meets; he is at Nauheim for the treatment of a heart problem but it’s unclear whether the ailment is real. He is Dowell’s opposite, a virile, physical, passionate man.
Leonora Ashburnham: Edward’s wife by a marriage that was more or less arranged by their fathers. Leonora comes to resent Edward’s philandering as much for its effect on her life as on her marriage and asserts more and more control over Edward until he dies.
Nancy Rufford: The young ward of the Ashburnhams; Edward falls in love with Nancy after he tires of Florence. Eventually Edward arranges for Nancy to be sent to India to live with her father, but she goes mad en route when she learns of Edward’s death.
La Dolciquita: A Spanish dancer (The Grand Duke's mistress) who is Edward's first sexual affair. Although he believes himself to be romantically attached to her, he quickly becomes disillusioned by her thirst for his money. She is not at all interested in Edward's "sentimental" gestures, and asks for money and expensive gifts in exchange for sex.
Maisie Maidan: Edward's third affair. Maisie was a young, pretty, married woman whom Leonora purchases from her "child husband" and brings back to Europe for Edward's sake. Maisie has a true heart defect and it takes her life as she tries to flee from Edward.