Recent studies have shown that complete blood count (CBC) parameters can effectively predict long-term mortality and re-infarction rates in acute coronary syndrome (ACS). However, the role of these parameters in predicting short term mortality has not been studied extensively. The main objective of this study was to determine whether CBC parameters can predict 30-days mortality and the incidence of major adverse cardiac event (MACE) in ACS patients.A total of 297 patients with ACS were recruited in this prospective study. The relationship of baseline white blood cell (WBC) to mean platelet volume ratio (WMR) with MACE and mortality was assessed during a 30-days follow up. The patients were divided into two groups: Group A [WMR<1000] and Group B [WMR>1000]. Multivariate COX regression was performed to calculate hazard ratios (HR).WMR had the highest area under receiver operating characteristics curve and highest discriminative ability amongst all CBC parameters in predicting mortality. Patients in Group B had a higher mortality rate (p<0.001) than patients in Group A. WBC count (p=0.02), platelet count (p=0.04), WMR (p=0.008), platelet to lymphocyte ratio (p<0.001) and neutrophil to lymphocyte ratio (p=0.03) were significantly higher in the MACE-positive group as compared to MACE-negative. In multivariate cox regression analysis, WMR>1000 (HR=2.9, 95% confidence interval 1.3-6.5, p=0.01) was found to be strongest biochemical marker in predicting mortality.WMR is an easily accessible and an inexpensive indicator, which may be used as a prognostic marker in patients with ACS.