We investigated the patterns and correlates of parents differential treatment of adolescent siblings in 246 two-parent Mexican American families. In home interviews, siblings rated 7 domains of differential treatment (e.g., privileges, chores, warmth) as well as their adjustment and perceptions of parental acceptance and fairness, and both parents and adolescents reported on cultural dynamics. More gender-typed patterns of differential treatment were evident when parents were more oriented to Mexican than Anglo culture. The links between differential treatment and youth reports of adjustment, parental acceptance, and parental fairness were moderated by adolescents' familism values, particularly for older siblings: Differential treatment was linked more strongly to adjustment and parent-youth relationship problems when youth reported lower levels of familism.