ABSTRACT Approximately 1 in 54 children in the United States is diagnosed with autism spectrum disorder (ASD). Among children with ASD, estimates of overweight and obesity (OW/OB) range from 19% to as high as 55% with the majority of studies reporting OW/OB rates equal to or greater than typically developing children. OW/OB in childhood tracks well into adulthood and is associated with negative health and psychosocial consequences. To date, the most successful treatment for typically developing children with OW/OB is family-based behavioral treatment (FBT), which delivers weekly group-based treatment to the parent and child separately over a 6- month period. However, children with ASD are typically excluded from these trials and given their unique presentation, require a tailored treatment program. FBT programs for parents without their child (Parent-based treatment [PBT]) are more appropriate for families with a child with ASD and OW/OB, as the functioning and language levels of the children can impact their ability to directly participate in an intensive group-based program. Research shows that PBT is noninferior to FBT on child weight loss and is less costly to implement. Our group has developed and pilot tested a PBT group for children with ASD and OW/OB (called PBT-ASD). Our pilot data showed that the PBT-ASD program was feasible, acceptable and showed initial efficacy on child weight loss. This project is the next step in this program of research, and we will recruit 150 youth with OW/OB and ASD and their parent and randomize them to a 6-month telehealth PBT-ASD or active health education comparator (HE). We will assess main outcomes in children and parents at five time points; baseline, mid- treatment (month 3), post-treatment (month 6), 6-month follow-up (month 12) and 12-month follow-up (month 18). The primary aim of this study is to compare the effect of PBT-ASD and HE on the target child’s weight (BMIz/%BMIp95) over the 18 months of the study. The secondary aim is to determine the extent to which the PBT-ASD and HE affect parent BMI, parent and child physical activity and dietary intake, child mealtime behavior, parenting style and self-efficacy. As an exploratory aim, we will evaluate moderators (e.g. parent and child gender, parent and child age, parent educational level, parent baseline BMI, child baseline BMIz/%BMI p95, parent executive functioning, parenting, child symptom severity, child adaptive behavior skills) and mediators (e.g. parenting, child symptom severity) of the PBT-ASD and the HE treatment on child BMIz/%BMI p95 over time. This program of research could advance the standard of practice for children with ASD, and could result in a tailored intervention for children with both ASD and OW/OB. We believe that by working with parents using a telehealth model, we can potentially provide an effective and durable treatment, which can easily be disseminated to parents with children with both ASD and OW/OB.