Sleep is essential for survival and humans spend approximately one-third of their life asleep. Adequate sleep is needed to maintain both physical and psychological health. Routinely getting less than the recommended amount of sleep for your age can have profound negative effects on health, such as increasing the likeliness of psychiatric illness, diabetes, cardiovascular disease and stroke. In children and adults with neurodevelopmental disorders, the prevalence of sleep disorders is significantly higher than in the general population. Given the relationship between sleep and psychiatric disorders, it is essential that psychiatrists have knowledge of the principles of sleep medicine. In this article, we focus on the common sleep disorders found in those with attention-deficit hyperactivity disorder (ADHD) and autism spectrum disorder (ASD) and give an overview of screening, diagnosis and management.