Introduction: Autism spectrum disorder (ASD) is characterized by core symptoms of social communication deficits and repetitive behaviors. Sleep dysregulation is increasingly recognized as an accompanying symptom of ASD, which may lead to, or exacerbate, core behavioral symptoms. The majority of studies investigating sleep in children with ASD use parental subjective measures to collect information about sleep (Elrod & Hood, 2015; Goldman et al., 2011); however, it is unclear whether parents' assessment of their children's sleep is consistent with objective ratings of sleep. This study investigated whether subjective parent ratings of their children's sleep and objective sleep equipment ratings varied across three groups of children (i.e., those with ASD, those with developmental disabilities (DD), and those who are typically-developing), such that ratings of parents in the ASD and DD groups would be closer to objective sleep ratings than the ratings of parents of typically-developing children. The study also examined adaptive behavior abilities and age as covariates in the relationship between parental subjective sleep ratings and objective sleep ratings. Method: Thirty-two children with ASD, 6 children with a DD, and 12 typically-developing children participated in an overnight PSG; a parent or guardian filled out a sleep questionnaire about that child's sleep habits. A two-step multivariate analysis of covariance (MANCOVA) tested between and within group effects. Results: Results of the MANCOVA analysis revealed non-significant differences in the discrepancy between subjective and objective sleep ratings of the three groups. Adaptive behavior was not a covariate. When age was included as a covariate, significant results emerged for ratings of total sleep time. Conclusions: Subjective parental ratings of sleep and objective ratings of sleep were not significantly different for any of the three groups, though overall, parents tended to overestimate their child's sleep time. Additionally, the ASD parents showed a trend in overestimating their child's sleep efficiency and under-rating the time until sleep onset. Implications for obtaining ratings of a child's sleep are discussed.