This article investigates one way in which humor plays effectively in environmental literature and ecocriticism. Does humor support environmental motivations or derail such agendas? Rhetorical theory suggests the former. By using the specific example of Barbara Kingsolver’s The Poisonwood Bible, we can determine whether or not Kingsolver integrates humor with her environmental agenda. The Poisonwood Bible exposes what Kingsolver views as failings in American policies and practices, and humor in four of the five narrators’ tellings wins over audiences that stated political agendas might otherwise repel. The four rhetorical functions of humor that rhetorician John C. Meyer proposes demonstrate how the environmentalist can use humor to simultaneously be polemical and build coalitions. Extended more broadly to aims of ecocriticism, Meyer’s theory supports the environmentalist agenda of classic ecocriticism and illuminates how humor can work within that framework. However, Meyer’s four rhetorical functions of humor are relevant to only one aspect of the poststructuralist “irreverent ecocriticism” that Nicole Seymour posits, which would have critics recognize absurdities in the critical enterprise. While Meyer’s theory would not fully support the enterprise of “irreverent ecocriticism,” it does illuminate how Seymour’s notion of “affect” can incorporate contradictory impulses yet be effective.