Diabetes mellitus (DM) is a complex disease with varying degrees of systemic and oral complications. The periodontium is also a target for diabetic damage. Diabetes is a pandemic in both developed and developing countries. In recent years, a link between periodontitis and diabetes mellitus has been postulated. The oral cavity serves as a continuous source of infectious agents that could further worsen the diabetic status of the patient and serve as an important risk factor deterioration of diabetes mellitus. The present review highlights the relationship between diabetes mellitus and periodontitis. The potential mechanisms involved in the deterioration of diabetic status and periodontal diseaseare also discussed.