The main aim of this review is to update the reader with practical knowledge concerning the relationship between diabetes mellitus and periodontal diseases. Exclusive data is available on the association between these two chronic diseases till date. Articles published on this relationship often provide the knowledge of definitions of diabetes mellitus and periodontal diseases, prevalence, extent, severity of periodontal disease, complications of diabetes along with the possible underlying mechanisms. The authors reviewed human epidemiological studies, cross-sectional observations and longitudinal cohort, case control that evaluated variables exclusively over the past 30 years and the predominant findings from the “certain” articles are summarized in this review. This review clarifies certain queries such as 1) Do periodontal diseases have an effect on the metabolic control of diabetes? 2) Does diabetes act as a risk factor of periodontitis? 3) What are the possible underlying mechanisms relating the connection between these two chronic diseases? 4) What is the effect of periodontal intervention on metabolic control of diabetes? After a thorough survey of literature, it was observed that diabetes acts as a risk factor in development of periodontitis as periodontitis is significantly aggravated in patients suffering from diabetes having long term hyperglycemia. Different mechanisms underlying the association between the accelerated periodontal disease and diabetes are emerging but still more work is required. Major efforts are required to elucidate the impact of periodontal diseases on diabetes. At the same time, patients are needed to be made aware of regular periodontal maintenance schedule and oral hygiene.