Mean platelet volume (MPV) is a simple and economical test that is easy to interpret and is routinely measured with automatic cell counters. It indicates platelet volume and platelet function and activation. Variations in platelet volume may occur more as a result of varying differentiation of megakaryocytes in association with production agents in bone marrow rather than of ageing of platelets in circulation. The purpose of this study was to evaluate the relation between mortality and changes in MPV values in patients hospitalized in the pediatric intensive care unit. We evaluated MPV1 levels at the first hour of hospitalization of patients monitored in the pediatric intensive care unit between February 2014 and February 2015, MPV2 levels at the 48th hour, Δ MPV (MPV2-MPV1) values PIM, PRISM, PELOD and PMODS values, diagnosis, age and sex. Fifty-four patients were female (45.4%) and 65 (54.6%) male. The mean age was 51.2 months m(range, 2-189 months). The mean PIM value was 35.4 ± 27.7, the mean PRISM was 18.5 ± 9.3, the mean was PELOD 21.3 ± 10.5, and the mean PMODS was 5.6 ± 3.0. Mortality was correlated with PIM, PRISM, PELOD and PMODS (p<0.001). Sixty-six (55.5%) patients survived. The standardized mortality rate (observed/expected mortality) was 0.99. The mean MPV1 was 9.5 ± 1.05 (range, 6.1-12.4) and mean MPV2 was 9.6 ± 1.15 (range, 6.5-12.5). There was a significant correlation between Δ MPV >0 and mortality (p<0.001). Mortality in patients with Δ MPV ≤0 was 21.4%, but 65.1% in those with levels >0. No correlation was determined between MPV1 and MPV2 and mortality (p= 0.480 and p= 0.213). Δ MPV>0, low levels of albumin and PRISM score were identified as independent risk factors for mortality.