This study explored the impact of parental sleep quality on the experience of behavior problems by children with autism spectrum disorder. A 14-day daily diary was used in a sample of 176 mother–father couples. Dyadic multilevel models were conducted to examine the between-person and within-person effects of previous-night sleep quality on parents’ rating of level of behavior problems by the child with autism spectrum disorder and level of positive and negative affect. Results indicated that persistently poor sleep quality was associated with between-person differences in initial rating of level of behavior problems by the child with autism spectrum disorder for mothers. At a within-person level, previous-night sleep quality moderated the association between rating of level of behavior problems by the child with autism spectrum disorder and level of positive and negative affect in fathers. Child-related stressors exerted less influence on fathers’ affect following a day with poor sleep quality. Interventions aimed at enhancing sleep quality in parents of children with autism spectrum disorder may have important effects on parental psychological well-being.