There is limited data about the bleeding complication of antiplatelet therapy after coronary artery bypass graft (CABG) operations focused on diabetic patients. Herein, we aimed to evaluate the effects of aspirin and clopidogrel monotherapies on postoperative bleeding in these patients. A total of 165 diabetic patients who underwent isolated off-pump beating heart coronary artery bypass (OPCAB) operation were evaluated, 84 patients were included in this retrospective study. Patients were divided into groups according to the type of antiplatelet regime. Chest tube drainage amounts and the amount of blood product transfusions were evaluated. Acetylsalicylic acid (ASA) - group included 42 aspirin monotherapy and Clopidogrel group included 42 clopidogrel monotherapy patients after propensity matching. The mean drainage amount in ASA - group was 670.24 +/- 185.46 mL, in Clopidogrel - group was 921.43 +/- 167.53 mL (p < 0.001). More packed red blood cell (PRBC) and fresh frozen plasma (FFP) units were needed in the Clopidogrel - group than in the ASA group (2.05 +/- 1.13 vs. 0.83 +/- 0.93 units of PRBC, and 1.90 +/- 0.58 vs. 1.05 +/- 0.58 units of FFP, respectively, p< 0.001). In conclusion, clopidogrel had a stronger effect on bleeding in diabetic patients than aspirin after OPCAB surgery.