The objective of this study is to determine whether the parent-child relationship exerts a mediating effect on the influencing relationship of the self-concept of children and adolescents with career maturity. To this end, we processed data from 5621 students who participated in the first through fifth rounds of the survey in the 2013 Korea Education Longitudinal Study. We performed a paired sample t-test to verify differences between the groups of children and adolescents. To verify the mediating effect of the parent-child relationship on the influencing relationship of self-concept among children and adolescents with career maturity. The results showed that there was a difference depending on gender and city size in terms of self-concept, career maturity, and relationship. This study also revealed a significant discrepancy in the self-concept and parent-child relationship based on the developmental stages. In addition, the study also verified the mediating effect of the parent-child relationship in the relationship between the self-concept of children and adolescents and their career maturity. Based on these findings, it is necessary to implement a systematic education program for parents because the parent-child relationship is highly important in improving students' career maturity.