Over forty percent of autistic children experience poor sleep quality, and social interaction difficulties are a core characteristic of autism. However, the relationship between sleep quality and social functioning and behavior remains poorly understood. This systematic review examined the evidence concerning the impact of sleep quality on the social functioning and behavior problems in autistic children and adolescents. It also identified key related factors and evaluated how this issue has been researched to date. Seven key journals were hand-searched and five databases were systematically searched, using keywords. Titles and abstracts of 4123 items were screened against eligibility criteria by two researchers. Relevant studies were retained if they were peer-reviewed empirical papers, published in English between 2000 and 2021. Then, the full text of 97 papers was screened and if they met the eligibility criteria, their reference lists were hand-searched. Forty-six studies were included in the final review. Data were systematically extracted and two authors critically appraised the strengths and weaknesses of studies using Critical Appraisal Skills Programme tools. Key themes were identified, because a meta-analysis was not possible due to the studies’ heterogeneity. The review identified that sleep quality and social functioning are associated with one another and there is a small amount of evidence that a bi-directional causal relationship may exist. Evidence suggests that several nights of suboptimal sleep duration and a lack of deep continuous sleep negatively impact externalizing and internalizing behavior. Sleep quality is also reduced by anxiety and sensory sensitivity. However, longitudinal studies with larger samples are needed to establish causality. Future research needs to examine confounding factors and to develop consensus regarding best-practice processes for the objective measurement of sleep with autistic children. Additional research also needs to further examine the consequences of poor sleep quality on internalizing behavior, and the impact of socio-cultural practices.