The purpose of this study was to investigate the effects of self-concept, self-determination, self-efficacy, self-future reliance, academic stress, parental attitude, achievement, and family academic status on the interpersonal relationship competency (relationship, leadership, collaboration) of adolescents. This study used the National Youth Policy Institute’s ‘A study on the measurement of Korean Youth Competency and International Comparison’ in 2017 (elementary, middle, high school). The number of 6 th grade participants was 882, the number of 9 th grade participants was 960, and the number of 12 th grade participants was 1,171. Results obtained from the analyses were as follows. First, relationship, leadership, and cooperation, which are sub-variables of interpersonal relationships, show a ‘yes’ level with scores of late 2 and early 3 on a 4-level Likert scale. Second, according to the results of multiple regression analysis, self-determination, self-efficacy, self-future reliance, and academic stress variables had a positive effect on relationship, leadership, and cooperation in all grades. Particularly, self-efficacy and self-future reliance were highly related to relationships, leadership, and cooperation. On the other hand, parental attitude only affected relationships in the 6 th grade of elementary school, but did not affect other grades and interpersonal relationship competency.