Introduction: Type 2 diabetes mellitus, due to its high incidence and mortality rates, is a major health problem around the world. Also, the type II diabetes is a type of metabolic disorder characterized by increased blood glucose, which is due to insulin resistance, insulin deficiency, or both. The current study aimed to assess the mean platelet volume (MPV) in type 2 diabetes patients compared to nondiabetics, and determine the correlation between MPV and fasting blood glucose, glycosylated hemoglobin (HbA1c). Methods: This case-control study was conducted on all patients (n = 120) diagnosed with diabetes referred to the clinical laboratory of Be'sat Hospital in Hamadan City, Iran, during 2015-2016. The patients were divided into the two groups of case and control (n = 60, each group). The mean platelet volume was measured by an automated blood cell counter. The blood glucose and HbA1c levels were also measured in both groups. Data were analyzed using the Chi-square, t test and Mann-Whitney tests with the SPSS software version 16. The significance level was equal to 0.05. Results: The mean age of the control group was 41.78 years and that of the case group was 41.58 years. The mean platelet volume was 8.42% in the case group and 7.74% in the control group, which showed a significant difference between the two groups (P = 0.001). The mean platelet volume in people with HbA1c less than 7 in the case group was less than those who had HbA1c more than 7 and this difference was statistically significant (P = 0.001). Conclusion: The mean platelet volume in diabetic patients was significantly higher than in the nondiabetic group. So, it seems that the elevated MPV can be used as a parameter for the diagnosis of vascular complications of diabetes.