Purpose: This study was designed to exam me the effects of an assertive training program on interpersonal relations, and psychiatric symptoms in patients with a mental disorder. Method: The study employed a quasi experimental design. The subjects included 44 patients with a mental disorder, 20 in the experimental group, and 24 in the control group. Data was collected using structured questionnaires over a 3 month period. Results: There were greater significant increases in scores of interpersonal relations and content of communication in the experimental group than the control group. Also, there was a greater significant decrease in the score of psychiatric symptoms in the experimental group than the control group. Conclusion: Assertive training has an effect on increasing content of communication and decreasing psychiatric symptoms.