Mean platelet volume (MPV) has been proposed as a marker of platelet reactivity and cardiovascular risk. Its prognostic significance has not been thoroughly investigated in patients with non-ST elevation acute coronary syndrome (NSTE-ACS). We included 1,041 consecutive patients with NSTE-ACS. Patients were divided in quartiles according to the MPV value on admission (fl) i.e. Q1<7.5; Q2=7.5-8.0; Q3=8.1-8.8; Q4≥8.9. The primary study endpoint was the composite of cardiovascular death and re-myocardial infarction (MI) at one year. Secondary study endpoints were individual cardiovascular death and re-MI. Patients in Q4 were older, had a higher prevalence of previous MI, peripheral artery disease and advanced Killip class compared to patients in Q1-Q3. Elevated MPV levels (Q4) was independently associated with gender, smoking status, platelet count and creatinine level. Overall, 210 patients (20.2%) reached the primary endpoint, 124 (12.1%) died from cardiovascular causes and 125 (12.0%) suffered from re-MI. On multivariable analysis patients in Q4 were at higher risk of primary endpoint (HR=1.41; 95%CI 1.06-1.89; p=0.02) whilst the association with cardiovascular death and re-MI was attenuated. MPV as continuous variable was independently associated with both primary endpoint (HR=1.19; 95%CI 1.06-1.33; p=0.003) and cardiovascular death (HR=1.23; 95%CI 1.06-1.42, p=0.006). The incorporation of MPV into a comprehensive model of risk significantly increased the likelihood ratio chi-square for prediction of both the composite endpoint (p=0.004) and cardiovascular death (p=0.009). Therefore, MPV may be useful to improve risk stratification in NSTE-ACS patients and should be included in future prospective studies evaluating the role of platelet function in promoting cardiovascular events.