Aim: Red blood cell distribution width (RDW) and epicardial fat tissue (EFT) are considered as a novel risk factor for cardiovascular disease. However, their relationship in patients with type II diabetes mellitus (DM) has never investigated before. Materials and Methods: Our study was a single-center prospective study which included 159 diabetic patients and 153 healthy controls. Two-dimensional and M-mode echocardiographic examination was performed using standard apical, parasternal, and subcostal views in all the study participants. Results: EFT thickness and RDW were found to be significantly higher in diabetic patients compared to controls (4.3 ± 1.1 mm vs. 3.7 ± 1.0 mm P = 0.001 and 13.5 ± 0.7 vs. 13.2 ± 0.9 P = 0.044, respectively). EFT thickness and RDW were positively correlated. RDW value of 13.55 predicted EFT thickness >5 mm with a sensitivity of 61.7% and specificity of 58.8% (area under the curve [AUC]: 0.649 and P = 0.001). HgA1C value of >7 predicted EFT thickness ≥4.15 mm with a sensitivity of 60.7% and specificity of 60.4% (AUC: 0.651 and P < 0.001). No correlation found between RDW and HgA1C (AUC: 0.554 and P: 0.169). Conclusion: EFT thickness increased in diabetic patients, independent of age, gender, waist circumference, body mass index, and it was correlated with RDW and HgA1C.