Insomnia in children is complex and frequently multifactorial. This review discusses the major categories of insomnia as well as common causes. The consequences of insomnia, including issues with mood, behavior, and cognition, are discussed. Sleep disorders are much more prevalent in certain pediatric populations, such as children with autism spectrum disorders. The evaluation of insomnia in children includes a focused history and examination and occasionally actigraphy or polysomnography. Behavioral and pharmacological therapies are discussed, as are future directions for research and clinical practice.