The Brexit referendum has led to uncertainty, which has threatened EU migrants’ resources, including their rights to reside, to run a business or access welfare. Cross-national political and legal resources that include citizenship rights can enable migrants’ access to health care, pensions, education and other welfare benefits, but these remain far from guaranteed. Using Conservation of Resources theory, we show how coping with uncertainty requires the mobilisation of individual and collective resources. We draw on 55 qualitative interviews to explore how three groups of EU migrants, entrepreneurs, Somali onward migrants and British retirees in Spain, respond to Brexit-related uncertainty. We examine the ways migrants utilise individual and social resources to respond to such uncertainty and explore their local, national and transnational coping tactics. Our data build on existing knowledge around the relationship between migration and uncertainty and enable the development of Conservation of Resources theory in relation to migration and transnationalism. We show how migrants draw upon wide-ranging transnational resources, which complement the local resources that are usually the focus of the theory. As such, we provide a useful mechanism to understand migration and uncertainty, which may have utility in considering other migration crises or stresses.