The primary goal of this study was to test how mother and adolescent proficiency in a common language moderates the link from parenting to adolescent development. A sample of Mexican‐origin fifth‐grade adolescents (N = 674, 50% female) was measured longitudinally on self‐control and aggression. Mothers were rated on observed positive discipline, warmth, and harsh discipline. Positive discipline and warm parenting predicted increases in self‐control and decreases in aggression, but only among mother–adolescent dyads who were proficient in a common language. Harsh parenting predicted decreases in self‐control and increases in aggression, but only among dyads who were not proficient in a common language. Similar results were found in a conceptual replication among a second sample of 167 Mexican‐origin adolescents.