Abstract Background: Cardiovascular complications are very com-mon in diabetic patients. Type 2 diabetic patients have elevated whole blood viscosity which is associated with these vascular complications. Aim of Study: To determine the effect of aerobic exercises on blood viscosity in type 2 diabetic patients. Methods: Thirty type 2 diabetic men included in the study from Kasr Al-Ainy Hospital and from outpatient clinics at Faculty of Physical Therapy Cairo University. Their mean ±  SD age, weight, height, BMI and HbA1c were 47.83±3.5 years, 91.8±5.82kg, 175.2±6.4cm, 29.69±2.1 (kg/m2) and 7.15±0.63% respectively. Whole blood viscosity was evaluated before and after the training program. All patients performed moderate aerobic exercise (65%-75%) in the form of treadmill exercise program 3 sessions per week for 8 weeks, the duration of the session was about 45 minutes and consist of warming up phase of slow walking on treadmill for 5 minutes (10%:20%), training phase 35 minutes and cooling down for 5 minutes (10%:20%). Results: There was a significant decrease in the total blood viscosity post-treatment and the percent of change was 4.56%. Conclusion: Aerobic exercise is a good way to reduce blood viscosity in patients with type 2 diabetes mellitus and this can help control vascular complications.