Contemporary consumer markets are characterized by both a heightened need for sustainability and an increasingly cosmopolitan lifestyle. This article bridges these two trends and studies two untapped questions: (1) How do cosmopolitan consumers relate to sustainable behavior? and (2) How should environmental messages be framed to successfully target cosmopolitan consumers? Four studies in three countries show that high-cosmopolitan consumers demonstrate environmental concern and engage in sustainable behavior. To successfully target this promising segment with sustainable products or messages to promote sustainable behavior, marketers and public policymakers should highlight the benefit of these products/behaviors for the global (rather than the local) environment. However, the findings also show that high-cosmopolitan consumers can be successfully targeted to support local environmental initiatives when activating their local identification. The article offers implications for businesses, non-government organizations, and public policymakers in designing effective messages to promote sustainable behavior.