Background: Many epidemiological studies discuss the relation between the ABO blood group and the risk of developing diabetes mellitus. ABO is the major blood group system. Diabetes mellitus is a metabolic disorder characterized by hyperglycemia. It is firmly considered that like other congenital characters and qualities blood types probably relate to diabetes mellitus. Materials and Methods: The study duration was 3 months from June to August 2021 study design was a comparative cross - sectional study. In our study, 400 participants were included: 200 were confirmed diabetics and 200 were non - diabetic as control. This study was conducted in the department of Pathology at Rehman Medical Institute, Peshawar. After obtaining informed consent from every patient 3ml of Blood samples in the EDTA tube were collected, labeled and sent to the laboratory for identification of blood group. Slide agglutination test for the determination of ABO and Rh blood groups was used. Results: It was observed that blood group B was significantly more common among diabetic subjects (p- value < 0.05). Our study shows a higher percentage of blood group B in the diabetic group (46.5 %) compared to controls (27 %). Conclusion: We conclude that there was an association between blood groups and Diabetes Mellitus. The outcomes suggest that the frequency of blood group B is significantly (P < 0.05) higher in type 2 diabetes as compared to non - diabetes.