The purpose of this study was to address gaps in the trauma treatment literature related to the expense and inaccessibility of evidence-based interventions for children with disabilities who have experienced trauma. Another aim of this study was to provide additional support for a newly piloted intervention for children with disabilities who have experienced trauma. This intervention is known as Smart Start: Parenting Tools for Children with Developmental Delay, Social-Emotional Concerns, and Trauma. A non-concurrent multiple baseline method was used to determine whether there was a functional relationship between the intervention and children’s challenging behaviors for five caregiver-child dyads. In addition, three of five caregiver-child dyads were assessed for improvements in child PTSD symptomatology, positive parenting practices, parenting stress, and treatment acceptability. Results from visual analysis, masked visual analysis, and hierarchical linear modeling were mixed, but generally supported a statistically and clinically significant relationship between participation in Smart Start and improved caregiver ratings of children’s challenging behaviors. Wilcoxon Signed-Rank test did not show statistically significant changes in interventionists’ ratings of challenging behavior, but descriptively, four of five children were rated as improved. Reliable change index scores revealed statistically significant changes in trauma symptoms and parenting stress for two participants. Positive parenting practices improved significantly for all participants according to the reliable change index. The intervention was implemented with good fidelity. All caregivers found Smart Start highly acceptable. Future research with larger samples is warranted based on the extremely promising results of the present study.