Insomnia disorder is one of the most prevalent conditions comorbid with diabetes and has been shown to have a possible role in the development of diabetes. Insomnia is characterized by a state of excessive physiological and cognitive arousal with alterations in autonomic and hypothalamic-pituitary-adrenal function. The chronic neuroendocrine activation in insomnia may predispose insomniacs to the development of metabolic disorders including glucose intolerance. In contrast, diabetic complications, in combination with the disruption of a sleep-wake homeostatic and circadian process, can be key factors precipitating insomnia symptoms and involve several subtypes of insomnia. Furthermore, inappropriate lifestyles are also likely responsible for the exacerbation of insomnia and diabetes. Thus, the pathogenesis of insomnia disorder and diabetes could mutually interact to develop each disease with a vicious cycle, accounting for the high comorbidity between the diseases.