Youth with Autism Spectrum Disorder (ASD) are at an increased risk for developing obesity when compared to their typically developing peers. Given higher prevalence of obesity in youth with ASD, understanding factors relating to success in obesity treatment provides insight into implementing efficacious treatments for youth. The current study examines age, sleep, and metabolic factors potentially affecting success in 74 youth (M[subscript age] = 11.66) attending a multidisciplinary weight management treatment program over a year. Multilevel modeling indicated that higher baseline BMI class category, medications at baseline, and absence of sleep difficulties predicted greater reduction in BMI after a year of treatment.