Mark Twain’s Adventures of Huckleberry Finn has often been read as a psychological novel, but the role of the concept of cognitive dissonance has not been fully explored. This articles explores the novel in terms of cognitive dissonance, showing how it drives the characters, especially Huck Finn. Huck’s relationship with Jim is a series of encounters with cognitive dissonance, culminating in the novel’s climax in Chapter 31. Cognitive dissonance can also explain the reactions of readers and critics, as well as explain society’s attitudes in Twain’s time and in ours.