Evidentials, as a grammatical means of overtly expressing information source, play a pivotal role in communication, cognition, and speakers’ status within a community. This accounts for their frequent spread in language contact situations. Evidentials often develop as a consequence of areal diffusion. A language surrounded by languages without evidential distinctions is likely to lose evidentials. Evidentials are among the defining features of a number of well-established linguistic areas, among them the Balkans, the Caucasus, and the Baltic region in Eurasia, and the Vaupés River Basin linguistic area in Amazonia. They have made their way into a number of contact varieties of major European languages, including Spanish and Portuguese. An obsolescent language may lose or restructure its evidentiality system depending on the dominant language speakers are shifting to. Further factors propitious for a spread of evidentials in language contact include multilingualism and shared discourse genres and speech practices.