Abstract In recent years, it has been widely witnessed that a surprising number of adolescents suffer emotional and mental health problems, and such turmoil is very often carried over into adulthood with serious implications for adjustment during the post-adolescent years. On this point, mental health problems in Korea are only now being considered crucial factors in the health status of adolescents and important public and social issues. It is also true that studies concerning the link between adolescents’ mental health problems and their psychology are limited. The purposes of this study were to investigate mental health problems of Korean adolescents, to reveal factors affecting their negative mental health and to explore a possible relationship between mental health problems and psychological variables. 2052 Korean adolescents selected randomly from junior high and high schools in Seoul, Korea were surveyed. Korean Symptom Checklist, Health Locus of Control Scale, Self-efficacy Scale and Self-esteem Scale were used to identify mental health problems and psychological variables of adolescents. Results indicated that Korean adolescents showed high prevalence in interpersonal sensitivity, depression, anxiety and hostility. In addition, the findings revealed that there were significant differences in adolescents’ mental health problems between gender and age. Furthermore, results revealed that the adolescents’ mental health problems were statistically correlated with psychological variables. This study provides significant information for the relatively unstudied Korean adolescents and also has the potential to influence the development of better mental health programs for adolescents.