The purpose of this study is to examine relationships among university students" self-differentiation, self-esteem and mental health. The subjects were 400 students of four universities in Busan and Gyungnam area. A questionnaire survey was done. The results of this study are as follows : First, the levels of university students" self-differentiation and self-esteem were high. Second, university students" self-differentiation and self-esteem were correlated positively. Third, the levels of university students" depression and anxiety were relatively low. It showed that the subjects" mental health of this study were not bad. Fourth, depression had no significant difference by gender. However, female students had higher anxiety than male students had. Fifth, university students" self-differentiation and self-esteem had negative correlation with depression and anxiety, and self-esteem played a role of mediating variable between self-differentiation and mental health. Sixth, family projection, family regression and self integration of self-differentiation had indirect influence upon the students" mental health through self-esteem, while cognitive-emotional function had direct influence upon mental health and had indirect influence upon mental health through self-esteem as well. In this study, university students" self-differentiation and self-esteem were found to be important variables having influence upon mental health, and self-differentiation had indirect influence upon mental health through self-esteem. Counselling intervention strategies should be established considering self-differentiation and self-esteem of the students who complained about their maladjusted emotion and human relation problems at schools. Also, programs enhancing self-differentiation and self-esteem of university students should be developed and the execution of these programs will be needed to help the university students who experienced mental health problems such as depression, anxiety and so on.