Background: Platelet (PLT) count and other indices have been studied for their prognostic value in sepsis and septic shock, but their results are inconsistent. This study aimed to determine the usefulness of PLT count and other PLT indices in prediction of mortality in these patients. Methods: 108 patients with clear evidence of sepsis or septic shock were enrolled. PLT count, mean platelet volume (MPV), plateletcrit (PCT), platelet distribution width (PDW) were measured on admission and daily for the 1^st 5 days following admission. Patients were followed during their ICU and hospital stay, and then categorized as survivors and non survivors. All data were statistically analyzed. Results: PLT count and other PLT indices were significantly different between both non survivors and survivors groups. At the 5^th day, ΔPLT count, PDW, MPV  were significantly different in non survivors compared to survivors, -27.16 ± 11.19, 0.34 ± 0.3, 0.7 ± 0.23 vs 23.18 ± 3.5, -0.14 ± 0.07, -0.37 ± 0.19, p value: 0.014,0.027 and 0.002 respectively while ΔPCT shows no statistical significance. The cutoff values of  PLT count, PCT, MPV, and PDW that predict mortality were 100,000 /ul, 0.10% 10.25fL, and 12%, with area under ROC (AUROC) were 0.94, 0.75, 0.97,0.96, and p value <0.001, 0.002 <0.001, and <0.001 respectively. Conclusion:  PLT count and PCT were significantly decreased while MPV and PDW were significantly increased during the ICU stay in non survivor patients. MPV of 10.25 fL and PLT count of 100,000 /ul could be used as cutoff values in mortality prediction.