Challenging the critical commonplace that Uncle Tom's Cabin is, in effect, a sentimental sermon, this essay takes the novel's relationship to preaching, one of the most culturally authoritative forms of speech in antebellum America, as itself an object of analysis. It shows that Stowe, eager to preach yet uneasy about violating gender norms, created a narrator whose sermonic interventions move steadily from the culturally feminine to the culturally masculine—from sentimentality to a dark and angry theological vision that pushed the boundaries of acceptable religious speech. Stowe's qualms about this bold appropriation of religious discourse appear most strikingly in the afterword to the novel as it ran in the National Era, an overlooked alternate ending that undercuts the novel's closing jeremiad. This essay also demonstrates how thoroughly Uncle Tom's Cabin critiques and silences male preachers—both proslavery and antislavery—and how liberally it puts sermons into the mouths of numerous “lowly” characters, strategies by which Stowe transfers the power to preach from the ordained clergy to ordinary people who speak their convictions across the lines of gender, class, and race. The novel's diverse challenges to antebellum preaching defied social and religious hierarchies with a brio that implicitly called for broader democratic empowerment. The radicalism of the novel's sermonizing becomes especially clear when juxtaposed with that of the fiery, ultra-liberal Theodore Parker, antebellum America's leading antislavery preacher.