Coronary artery ectasia (CAE) is frequently considered to be an incidental angiographic finding; however, several reports have shown an association with myocardial ischemia and infarction. In this study, we aimed to evaluate the mean platelet volume (MPV), which is a marker of platelet reactivity, in patients with isolated CAE. In this study we investigated the platelet functions by MPV measurement in patients with isolated CAE. The study population consisted of 23 patients (17 males, 6 females) with isolated CAE (Group-I). Sex-age matched 30 patients (22 males, 8 females) with angiographically proven normal coronary arteries served as the control group (Group-II). Serum total cholesterol, HDL-C, LDL-C, triglyceride level, hemoglobin, white blood cell count, CRP, platelet count and MPV were compared in both groups. There was no significant difference between two groups in terms of age, gender, body mass index, blood pressure and heart rate. Serum total cholesterol, HDL-C, LDL-C, triglyceride level, hemoglobin, white blood cell count, platelet count were also similar in both groups. However, the MPV values of patients with isolated CAE were significantly higher than those of controls (P < 0.0001). In addition to that, CRP levels were found to be significantly higher in patients with isolated CAE (P < 0.002). Increased MPV may indicate the altered platelet reactivity and aggregation and thereby may be associated with ischemic events, observed in patients with isolated CAE.