The words of different languages partition the world in strikingly different ways. Yet many people are unaware of such differences, believing that some of the words of their native language pick out discrete categories based in nature. We investigated whether knowledge of cross-linguistic semantic diversity—putatively inherent to bilingualism—can reduce such essentialist beliefs. In three experiments, we found (a) that bilinguals were less likely than monolinguals to judge membership for animal categories in essentialist terms, (b) that explicit exposure to cross-linguistic semantic diversity, independent of bilingualism, yielded similar effects, and (c) that this manipulation reduced essentialist beliefs about social categories as well. Together, our findings suggest that learning about how languages differ in their semantic systems—a form of metalinguistic knowledge—can lead people to think about categories more flexibly. Implications for research on language and thought, and for ameliorating the negative consequences of social essentialism, are discussed.