Aim: We investigated the association of mean platelet volume (MPV) with the degree of retinopathy in patients with diabetes mellitus (DM). Methods: Ninety patients with diabetic retinopathy (DRP) and 30 healthy individuals were included in the study. Diabetic patients included 30 background, 30 non-proliferative and 30 proliferative diabetic retinopathy cases. Complete blood count, intra- and intergroup comparisons of MPV values were performed. Results: Mean values for MPV in patients with background, nonproliferative and proliferative DRP were 7.76±0.72 fL, 7.94±0.61 fL and 8.18±0.89 fL, respectively. MPV values of patients with background DRP was not significantly different from that of the control group and patients with non-proliferative and proliferative DRP as well. However, MPV values of patients with proliferative DRP were significantly higher than the values of control group (p< 0.05). A significant correlation was found between the degree of retinopathy and mean values of MPV in diabetic patients (r= 0.214, p< 0.05). Conclusions: We found an association between the degree of retinopathy and mean values of MPV. This finding suggests a role for platelets in the pathogenesis of vascular complications and that mean platelet volume would be useful in monitoring the disease progression.