Coparenting relationship has been linked to the development and adaptation of adolescents. However, whether and how fathers and mothers’ individual behaviors in coparenting relationships are linked to peer outcomes of boys and girls during adolescence have yet to be clarified. The present study addresses this gap in knowledge by examining the relationships among coparenting behavior, parent–adolescent attachment, and peer attachment of adolescents and the gender differences of these relationships. Families (N= 820) that included fathers, mothers, and focal adolescents (53% female, Mage = 13.70 ± 2.51) participated in this study. The fathers and mothers reported their coparenting behavior to their spouse and the adolescents completed the Inventory of Parent and Peer Attachment. Structure equation modeling in the total sample revealed that maternal positive and paternal negative coparenting behaviors were related to peer attachment through the indirect effects of father– and mother–adolescent attachments. Multi-group analysis revealed that father– and mother–adolescent attachments had strong predicting effects on the peer attachment of offsprings with the same sex. Maternal positive coparenting behavior was related to the peer attachment of boys and girls through the indirect effects of the father– and mother–adolescent attachments. Paternal negative coparenting behavior had a double-edged effect on girls’ peer attachment and was not related to boys’ peer attachment. This study extended the perspective of a family–peer system linkage by providing evidence that parents’ individual behavior in the coparenting process was linked to adolescents’ peer outcome. Moreover, this research suggested that encouraging mothers to enhance their positive relationship with fathers and preventing fathers from overtly pursuing conflicts and covertly disparaging mothers may be effective methods to promote adolescents’ peer relationships.