This study evaluated the impact of a preventive intervention program focused on self-understanding and interpersonal interactions to prevent psychosocial distress among Japanese university students. Two hundred and twenty-two undergraduate students were divided into a treatment group and a control group to complete Time 1 and Time 2 surveys. The intervention program included eleven weekly sessions covering self-understanding, self-control, interpersonal relationships, problem solving, conflict resolution, and stress management. Both female and male students in the treatment group reported a significant increase in social self-efficacy in interpersonal relationships from Time 1 to Time 2, but no significant changes were noted in the control group. Anxiety significantly decreased from Time 1 to Time 2, and no difference in depression was noted in the female treatment group, although anxiety and depression significantly increased in the female control group. The intervention program effectively prevented some aspects of psychosocial distress. (Contains 2 tables and 4 figures.)