BACKGROUND: In the present study, we evaluated the effectiveness of a parent training (PT) program in Japan for parents of adolescents with developmental disorders (DDs). In Japan, there were no separate programs for parents of children with DDs in early adolescence and beginning to assert their independence from their families despite the many parent-child conflicts and secondary disorders arising from the children. METHODS: The parents of forty-four adolescent children ranging in ages from ten to seventeen were assigned to either a control group or an experimental group. The program comprised two hour biweekly sessions for three months. The program we examined in this program are: how to praise, stress management for parents, cognitive restructuring, how to scold, problem-solving communication training and how to make a behavior contract. To compare the effectiveness of this program in the control and experimental groups, two-way analysis of variance was used to analyze data collected using psychological assessment scales such as the Strengths and Difficulties Questionnaire (SDQ), the Child Behavior Checklist (CBCL), the Conflict Behavior Questionnaire for Parents (CBQ), and the Beck Depression Inventory (BDI-II). RESULTS: The results showed a significant difference between pre- and post test scores on CBCL, BDI-II, and CBQ, but not on SDQ. The findings indicate that children’s behavioral problems and parent-child conflict in the experimental group were improved at the end of the program. CONCLUSION: Accordingly, special programs are needed for adolescent PT as well as PT programs for children with DDs.