Prior research suggests a link between academic performance and alcohol use during adolescence, but the degree to which this association reflects actual protective effects continues to be debated. We investigated the role of genetic factors in the association between academic achievement and adolescent alcohol use and whether achievement might constrain the translation of genetic influences on drinking into actual behavior (a Gene × Environment interaction). Analysis of twin data from Add Health (n = 399 monozygotic and dizygotic twin pairs) revealed not only common genetic factors underlying the association between achievement and alcohol consumption but also evidence for a gene--environment interaction. Specifically, the protective effect of achievement operated by moderating heritability of alcohol use, which was particularly salient for adolescents at high genetic risk for alcohol use.