International migration can promote development in both origin and destination countries. We hypothesize that migrant integration in destination countries is an important constraint on these gains. Using a randomized controlled trial, we study the effects of a low-cost, scalable digital intervention designed to reduce information frictions among Cape Verdean immigrants in Portugal. Access to the intervention improves migrants’ labor market outcomes, legal status, social integration with native-born individuals, and aspirations. These integration gains generate international spillovers, increasing political participation and leading to more egalitarian gender norms in the migrants’ origin-country. Leveraging variation in official destination country electoral data, we show that political participation transmits through increased exposure of better-integrated migrants to prevalent local norms at destination. These international turnout spillovers are weaker in localities with higher far-right support, consistent with a less migrant welcoming political climate attenuating norm diffusion.