Sleep problems are common in autism spectrum disorder (ASD) and attention deficit hyperactivity disorder (ADHD). Sleep problems in these disorders may not only worsen daytime behaviors and core symptoms of ASD and ADHD but also contribute to parental stress levels. Therefore, the presence of sleep problems in ASD and ADHD requires prompt attention and management. This article is presented in 2 sections, one each for ASD and ADHD. First, a detailed literature review about the burden and prevalence of different types of sleep disorders is presented, followed by the pathophysiology and etiology of the sleep problems and evaluation and management of sleep disorders in ASD and ADHD.