Objective: We have previously reported the modified parent training of smaller groups and shorter schedules (PTSS). In this study, we applied PTSS to the mothers of children with pervasive developmental disorder (PDD) and revealed the new evidence for its effectiveness. Methods: The participants were 30 mothers of children with PDD aged from 4.2 to 9.6 years. The effectiveness of PTSS was assessed with the confidence degree questionnaire (CDQ) and the child behavior checklist (CBCL), before and after each PTSS course. The recorded interviews were qualitatively analyzed using the KJ (Kawakita Jiro) methods. Results: Average CDQ scores were clearly improved as previously reported. In addition, the CBCL total T-score was significantly improved, which was not observed in the previous study. About KJ methods, six factors that change of mothers recognition were identified. Conclusions: Our findings provides additional evidence for the usefulness of PTSS for children with PDD.