Onset, progression, and management of type 2 diabetes mellitus remain a major challenge worldwide. Given the numerous accompanying complications and comorbidities, with high mortality rates and increasing healthcare costs, a comprehensive understanding of all strategies to address the incidence rate of type 2 diabetes mellitus is absolutely essential. Sleep is an influential and modifiable lifestyle behavior, and high-quality sleep prevents diabetes mellitus. This article explores in depth current evidence relating to the associations between sleep and diabetes, such as sleep hormones, circadian rhythms, sleep quality, and obstructive apnea. Understanding the relationship between sleep and diabetes mellitus enables strategies to be developed that can improve sleep quality. This article therefore provides information regarding clinical care, community care, and policymaking.