We examine the relationship between parental ethnic identity and cognitive development in ethnic minority children. This aspect of parental identity may shape children's cognitive outcomes through a direct influence on parenting behaviour, or by mediating parental access to social resources. Drawing an ethnic minority sample from a detailed UK cohort study, we find a negative association between maternal majority identity and children's cognitive test scores. This result is driven by poor households, by those who lack local family support networks, and by those who mostly speak a foreign language at home. We suggest that differential access to social resources is the most persuasive explanation of this result. Differences in parenting behaviour do not seem to play an important role.