In recent years, migration has become an important policy priority within and beyond the European Union. While the discourse that surrounds the contemporary migration policy agenda is one of the technocratic migration management, this overarching narrative conceals an underlying goal of prevention. Preventive efforts are increasingly geared towards stopping migratory movements before they have even begun. The effectiveness of such an approach remains contested and unclear. This article builds on the theoretical work of Czaika and de Haas (Population and Development Review, 2013, 39, 487) to explore the limits of prevention strategies designed to change minds, alter plans and redirect behaviours. It does so by drawing on insights from our own research into migration decision-making, alongside wider literature on individual sense-making, and connecting these to ongoing debates around policy effectiveness. In doing so, we show how the nature of localised encounters between ‘target’ populations and implemented policies can create potential sources of policy failure.