Background/Methods <p>Children with developmental disabilities (DDs) face behavioral, emotional, and social challenges that impact family dynamics. We aimed to investigate the feasibility and effectiveness of the Group Stepping Stones Triple P (SSTP) for South Korean families of children with DDs. Eight parents participated in six online group sessions and three individual phone sessions, supported by a behavior-tracking mobile app. To measure feasibility, satisfaction with the intervention and mobile application, along with participant retention rate, were assessed. Data were collected at three time points to assess behavior problems, quality of life (QoL), parenting stress, efficacy, and parent-child relationships. Wilcoxon signed–rank test was conducted.</p> Results <p>Participants reported high satisfaction with the intervention and offered suggestions for enhancement. There were no significant improvements between pre- and post-intervention. However, significant improvements in children’s behavior and QoL, parenting efficacy, positive parenting skills, and parent-child relationships were observed at the one-month follow-up. Some individual score change trends were also observed over time.</p> Conclusion <p>This study is the first to conduct Group SSTP in the South Korean context. The results suggest Group SSTP’s potential to address behavioral issues of children with DDs and improve parenting practices, supporting its broader application in healthcare settings.</p>