We examined the longitudinal relations among parental socialization practices—including acceptance or harsh parenting and ethnic socialization—ethnic identity, familism, and prosocial behaviors in a sample of U.S. Mexican youth. Participants included 462 U.S. Mexican adolescents (Mage at Wave 1 = 10.4 years old; 48.1% female), their mothers, and fathers at the 5th, 7th, 10th, and 12th grades. Results showed that maternal and paternal ethnic socialization predicted several forms of prosocial behaviors via ethnic identity and familism. Fathers’, but not mothers’, harsh parenting and acceptance had direct links to specific forms of prosocial behaviors. This study suggests the need for culturally informed theories that examine the reciprocal relations between two distinct domains of cultural socialization.