How does a state’s marginalization of borderland communities influence their sense of belonging? We argue that, in unstable regions in the Global South, such marginalization reinforces people’s sense of belonging to a transnational community. As we demonstrate, two causal mechanisms account for this process: the marginalization enhances (i) the border’s “disguising” quality that muddies diverse forms of insecurity and (ii) the border’s “facilitating” quality that permits certain actors and activities to cross borders while stopping others. Consolidation of people’s sense of belonging to a transnational community has implications for the state, as losing part of its citizenry to this transnational community undermines its own authority and the state–society relationship. Drawing on the case of the Colombian–Venezuelan borderlands, we substantiate our argument through evidence collected during in-depth fieldwork, including interviews and focus groups with peasants and other residents from remote borderland regions as well as with state and civil society stakeholders. We contribute to scholarship on identity and sense of belonging by theorizing its link to marginalization in the context of international borders. We further contribute empirically by documenting little-known cross-border practices and activities of residents of the shared border region of the Colombian department of Cesar and the Venezuelan state of Zulia.