Background:Mean platelet volum to platelet count (MPV/Plt) ratio (MPR) is a new predictor of mortality in critical patients with COVID-19 infection in intensive care unit (ICU). Objective:To retrospectively examine the laboratory predictors of mortality among COVID-19 patients. Materials and Methods:A total of 106 patients with COVID-19 in ICU were enrolled in the study.The medical records of the patients and the electronic patient monitoring system were retrospectively analyzed. Results:The Interleukin-6, C-reactive protein (CRP), procalcitonin, leukocyte count, neutrophil count, neutrophil %, neutrophil count/lymphocyte count (NLR) and neutrophil count/albumin (NAR) ratio was significantly higher among nonsurvivors (p=0.0001, p=0.004, p=0.003, p=0.049, p=0.007, p=0.009, p=0.007 and p=0.0001; respectively).While the survivors had lower platelet distribution width, red blood cell distribution width, MPV and MPR (p=0.016, p=0.03, p=0.005 and p=0.049; respectively), hemoglobin, Plt, mean corpuscular hemoglobin concentration, lymphocyte % ve monocyte % were higher (p=0.022, p=0.033, p=0.042, p=0.008 and p=0.04; respectively). In the logistic regression analysis, five features, including high levels of CRP, procalsitonin, pro-BNP, MPR, and low level of plt were shown as mortality predictors for COVID-19 patients in ICU (p=0.045, p=0.025, p=0.017, p=0.027 and p=0.041; respectively). Conclusion:Mean platelet volum to platelet count ratio, NLR, NAR predict mortality in critical cases of COVID-19 which will contribute to early prediction, accurate diagnosis, and treatment to improve the prognosis of patients. Keywords: COVID-19, mortality, MPV, MPV/platelet ratio, NLR, platelet