Coparenting conflict, which refers to the conflict between parents regarding parenting, has played a central role in children’s development and adjustment. The perspective of family and peer systems linkage has suggested that coparenting conflict is linked to peer-related development, but this view has yet to be clarified. This study aimed to investigate the relationships among coparenting conflict behavior, parent–adolescent attachment, and social competence with peers as well as the developmental differences of these relationships in early, middle, and late adolescence within Chinese families. Families (N = 808) that included fathers, mothers, and focal adolescents (53% female, Mage = 13.66 ± 2.53) participated in this study. Fathers and mothers reported their coparenting conflict behaviors separately, and the adolescents rated parent–adolescent attachment and social competence with peers. Results showed that fathers’ overt coparenting conflict behavior was related to social competence with peers through the indirect effects of father– and mother–adolescent attachments, whereas mothers’ covert coparenting conflict behavior was related to social competence with peers through the indirect effect of mother–adolescent attachment in the total sample. The multigroup analysis revealed that these relationships were significant in early and late adolescence. In addition, fathers’ covert coparenting conflict behavior was related to mother–adolescent attachment in late adolescence and all the relationships were insignificant in middle adolescence. The findings support the systematic perspective of family–peer system linkage and highlight the gender differences of parents in the effects of coparenting conflict on social competence with peers and the developmental differences during adolescence.