Challenging behaviors are a known predictor of high parenting stress in families of children with autism spectrum disorders. However, few studies have evaluated the effect of reducing challenging behaviors on parenting stress. The purpose of our study was to (a) examine the impact of reducing the frequency and severity of challenging behaviors on parenting stress and (b) compare the effects of family-centered support and parent education on changes in parenting stress. Both high severity of autistic symptoms and of challenging behaviors were predictors of parenting stress. Furthermore, receiving family-centered support were associated with larger reductions in parenting stress. Overall, our results suggest that reducing challenging behaviors with family-centered support may be preferable to produce collateral reductions in parenting stress.