We estimate the wage effects of bilingual education for the first time using a reform that introduced bilingualism in Catalan schools. Variation across years of schooling and birth cohorts provides identification. We find substantial returns to bilingual education. Effects worked through increased Catalan proficiency for Spanish speakers, but there were also positive impacts for Catalan speakers with less educated parents. The evidence suggests that findings are consistent with human capital effects rather than with increased search efficiency or reduced discrimination. Using the heterogeneous effect of the reform as instrument for language skills, we find sizeable returns to proficiency in Catalan.