Objective: This study examined the relationship between maternal beliefs on social development, management strategies of peer relations, and their child’s peer competence in order to understand how to promote children’s peer competence. Methods: Self-report questionnaires were used on 195 mothers with children four to years old. Data were analyzed using Pearson Correlation Analysis and Baron and Kenny’s three-step regression. Results: First, there was a positive relationship between maternal beliefs on social development and their child’s peer competence. Second, this study found that there were partial mediating effects of advice·support and supervision on the relationship between maternal beliefs on social development and children’s social competence. Conclusion/Implications: The findings confirm that mothers’ beliefs on social development and management strategies of peer relationships are proceeding factors for children’s peer competence. Significant attention should be paid to mothers’ beliefs on social development and management strategies of peer relationships for children’s positive social development.