The current study was aimed to examine the association between mean platelet volume (MPV) and risk for adverse clinical outcomes in patients with chest pain discharged from internal medicine wards following ACS rule-out. Included in the study were 12,440 patients who were divided into 3 groups according to MPV. The composite endpoint of 30-day all-cause mortality and hospital admission for ACS occurred more frequently among patients with high MPV. Each 1 point increase in MPV was associated with an 18% increase in the risk for the composite endpoint (p=0.02).Considering patients with MPV<7.8fl as the reference group yielded adjusted hazard ratios for the composite endpoint that were significantly higher in patients in the high MPV tertile (>8.8 fl) (HR 1.6, 95%CI=1.1- 2.5, P=0.04). We conclude that high MPV was associated with an increased risk of death and ACS among patients with chest pain who were discharged from internal medicine wards.