Daisy Miller - A rich, pretty, American girl traveling through Europe with her mother and younger brother. Daisy wants to be exposed to European high society but refuses to conform to old-world notions of propriety laid down by the expatriate community there. In Rome, she becomes involved with an Italian man named Giovanelli, and she eventually dies from malaria as a result of being outside with him at night. Along with Winterbourne, Daisy is the novel’s other possible protagonist.

Winterbourne - A young American who has lived most of his life in Geneva. Winterbourne is the novel’s central narrative consciousness and possibly the protagonist. He is initially intrigued by Daisy because of her frivolity and independence, but he eventually loses respect for her. After she dies, however, he regrets his harsh judgment and wonders if he made a mistake in dismissing her so quickly.

Randolph Miller -  Daisy’s younger brother. Randolph is a loud, ill-mannered, ungovernable little boy of about nine or ten.

Mrs. Miller - Daisy and Randolph’s vague, weak, ineffectual mother. Mrs. Miller seems obsessed with her health and is utterly incapable of governing the behavior of her children. She is silly and clueless, but when Daisy falls ill, she proves “a most judicious and efficient nurse.”

Mrs. Costello - Winterbourne’s aunt, a shallow, self-important woman who seems genuinely fond of Winterbourne. Mrs. Costello is the voice of snobbish high society. She also fulfills the role of “confidante,” a frequent figure in Henry James’s novels.

Eugenio - The Millers’ supercilious interpreter/guide, often referred to as “the courier.” Eugenio has better judgment and a greater sense of propriety than either Daisy or Mrs. Miller and often treats them with thinly veiled contempt.

Mrs. Walker - A wealthy, well-connected American widow who lives in Rome, knows Winterbourne from Geneva, and has befriended Daisy. Mrs. Walker shares the values of the rest of the American expatriate community, but she genuinely seems to care what happens to Daisy and tries to save her.

Mr. Giovanelli - An Italian of unknown background and origins. Mr. Giovanelli’s indiscreet friendship with Daisy is misinterpreted by the American expatriate community and leads, directly or indirectly, to Daisy’s ostracism and death.