This study examined parental warmth as a mediator of relations between mothers’ and fathers’ perceptions of dyadic coping and adolescent externalizing outcomes. Data from 472 adolescents, mothers, and fathers were collected over a three-year period from families in China, Kenya, Sweden, and Thailand. For mothers in all four sites and fathers in three sites, better parental dyadic coping at youth age 13 years predicted higher levels of parental warmth at youth age 14 years. For mothers in all four sites, higher levels of maternal warmth were in turn related to less youth externalizing behavior at the age of 15 years, and higher levels of dyadic coping at youth age 13 years were related to less youth externalizing behavior at the age of 15 years indirectly through maternal warmth. Emotional Security Theory helps explain the process by which dyadic coping is related to adolescent externalizing behavior. The results have important implications for parent- and family-based interventions.