Sleep problems are common in individuals with autism spectrum disorder (ASD). How sleep problems reflect specific ASD phenotypes is unclear. We studied whether sleep problems indexed functional impairment in a heterogeneous community sample of individuals with ASD. We analyzed 977 probands (233 females; age = 11.27 ± 4.13 years) from the Rhode Island Consortium for Autism Research and Treatment dataset, a unique public–private-academic collaboration involving all major points of service for families in Rhode Island. We found that individuals with a confirmed diagnosis of ASD were more likely to have sleep problems. However, across the whole sample and above and beyond a formal diagnosis, sleep problems were dimensionally associated with worse social impairment and poorer adaptive functioning. By using a large dataset reflective of the diversity of presentations in the community, this study underscores the importance of considering sleep problems in clinical practice to improve adaptive functioning in individuals with ASD.