Sleep, which was previously not a topic for discussion in clinical practice, is now a problem that cannot be disregarded in people with diabetes mellitus. Instead, the importance of sleep has increased for the management and prevention of diabetes mellitus. Diabetes mellitus and dyssomnias are both chronic conditions that have a significant effect on the quality of life and health. Numerous research has shown that the relationship between diabetes mellitus and sleep is bidirectional rather than linear. In this review, not only the effects of diabetes mellitus on sleep, but also the effects of sleep on diabetes mellitus are investigated, and the biological mechanisms are summarized as well.