Isabel Archer is a young woman of great imagination, resolve, and intelligence, but she lacks experience and wisdom. She treasures her independence and wishes above all to maintain her liberty, turning down two good offers of marriage in favor of the freedom to explore the world. She is overly confident in her own judgment, however, and her naïveté quickly becomes clear as she is easily manipulated by Madame Merle into marrying Osmond. It is through her suffering in a miserable marriage and witnessing her husband's disregard for her or her stepdaughter's happiness that Isabel learns how mistaken she was about him and regrets not heeding the warnings of her friends and family. Isabel remains committed to her responsibilities to the last, however.
Madame Merle is a cunning woman of many talents, much refinement, and numerous social connections, who sees Isabel's fortune as a means to an end. She skillfully manipulates Isabel into marrying Osmond, Madame Merle's old lover and father to their illegitimate daughter, in order to provide money for Pansy.
Gilbert Osmond is a collector of fine things who calls Italy his home. He has no real profession and subsists on a modest income. He is incapable of real love, although he comes closest with his daughter, Pansy, whom he treasures, much like one of the pieces of art that decorate his home. He stores her away in a convent. Osmond agrees to meet Isabel only at Madame Merle's suggestions that he should marry her to provide for Pansy. Isabel turns out to meet Osmond's strict standards, although he wishes she didn't have so many of her own ideas. He ultimately comes to hate her for her independence and disobedience, although it seems she cannot escape him.
Ralph Touchett is the son of a wealthy banker, and although he is American, he has lived in England most of his life. Because of his father's wealth and his own ill-health, Ralph has no real job and does not take over the bank when his father retires. Ralph loves his cousin Isabel and might have tried to marry her if his health didn't threaten him with an early death. He comes to see Osmond as a villain and warns Isabel not to marry him. He is shocked when she does, and the two drift apart. They are reunited on Ralph's deathbed when he tells her he adores her.
Lord Warburton is a wealthy member of the British aristocracy and neighbor of the Touchetts. He has misgivings about the justice of his position and vast property, although his political views are not so radical as to act upon his convictions by giving up any of his homes, land, or title. He falls in love with Isabel, later pursues Isabel's stepdaughter, and ultimately becomes engaged to a British woman. It seems he never stops loving Isabel, though.
Caspar Goodwood is the son of a cotton-mill owner and a smart, capable young man. He is hopelessly in love with Isabel, who refuses him time and time again. He persists in pursuing her, even though she tells him to leave her alone. Although he says he doesn't want to curtail her freedom, Caspar is possessive. He aggressively embraces her, and tells her he doesn't care if society condemns them, if only she will leave her husband. He wants to help Isabel.