Cross-border cooperation has contributed to the prosperity of many European regions, but it has also prompted cross-border migration flows, economic inequality, and segregation. Policy-makers have attempted to address the negative externalities of cross-border cooperation through various policies applied to arbitrarily-defined territories. Cross-border regions thus represent an analytically advantageous setting to study how attitudes change under strong exposure to migration, and how mezzo-level economic conditions and public policies may mitigate or enhance this attitudinal change. To test hypotheses derived from the contact theory and theory of group threat, this paper employs the longitudinal and geospatial dimensions of the German Socio-Economic Panel and the Swiss Household Panel. The causal identification leverages the regression discontinuity design and examines the effect of migratory events and cross-border public policies on attitudes towards migration between 1990 and 2018. The results of this project yield important insights into the migration-attitudes nexus and have policy implications for cross-border administrations.