Objective: The purpose of this study is to investigate the impact of maternal parenting stress on children's social competence, mediated by parenting efficacy and parent-child interactions. Methods: This study analyzed data from 1,484 households in the Panel Study on Korean Children (PSKC) using validated scales. The associations between maternal parenting stress (at age 5) and social competence (at age 9) were tested, followed by a dual mediation analysis of parenting efficacy (at age 6) and parent-child interaction (at age 7). Results: Parenting stress at age 5 negatively affected children’s social competence at age 9. The association between parenting stress at age 5 and children’s social competence at age 9 was mediated by reduced parenting efficacy at age 6 and weaker parent-child interactions at age 7. Conclusions: The results of this study indicate that starting prevention and early interventions for parents when their children are 5 years old may be beneficial. Particularly, gender-sensitive programs and programs to reduce parenting stress, while enhancing parenting efficacy and parent-child interactions, would be crucial for supporting children's social development.