Emerging evidence suggests that physical activity may be associated with improved sleep in autistic children. We aimed to determine whether physical activity associated with sufficient sleep duration in children and whether this association was modified by reported autism spectrum disorder (ASD) status. We analyzed existing data of children 6-17 years old whose caregivers completed the 2018 National Survey of Children's Health (nonautistic N = 20,845; ASD N = 681). Logistic regression determined whether physical activity (days active in the past week) associated with sufficient sleep duration. Physical activity-by-ASD interactions were included to determine whether the association differed for autistic children. Physical activity-by-ASD-by-sex and physical activity-by-ASD-by-age-group interactions were also modeled. Physical activity was associated with increased odds of sufficient sleep duration (e.g. 0 days vs 4-6 days: odds ratio (OR) = 1.85; 95% confidence interval (CI): 1.48-2.32). We did not observe an overall statistically significant interaction between physical activity and reported ASD status; however, the positive association between physical activity and sufficient sleep duration was weaker in autistic children, especially those with more severe ASD, female autistic children, and autistic children ages 6-12 years old. In conclusion, physical activity is a promising approach to improve sufficient sleep duration but with nuanced findings in autistic children.