The present study aims to investigate the effect of the predictive value of Neutrophil to Lymphocyte Ratio (NLR) and several routine laboratory tests on mortality in patients with positive Coronavirus disease-2019 (COVID-19) tests who were treated at Istanbul Training and Research Hospital. Routine laboratory data of patients with positive COVID-19 Real Time-Polymerase Chain Reaction (RT-PCR) results were obtained via the hospital information system. The laboratory tests included ferritin, C-reactive protein (CRP), lactate dehydrogenase (LDH), aspartate transaminase, creatinine, urea, D-dimer, neutrophil, and lymphocyte count. The number of patients was 2774 and they were admitted to Istanbul Training and Research Hospital between March 10 and June 10, 2020. The statistical data were obtained using SPSS 17.0 ver- sion. The patients were divided into two groups, one for mortality (n= 74 patients) and the other for non-mortality (N=2700 patients). In both mortality and non-mortality groups, the ratio of males was higher than females and the difference was not significant (p>0.05). 87.8% of those who lost their lives were treated in the intensive care unit (p<0.05). All parameters were statistically significant between mortality and non-mortality groups (p<0.05). In patients with mortality, diabetes mellitus, hypertension, chronic obstructive pulmonary disease (COPD), malignity, kidney failure, immunosuppressive treatment, and COVID-19-associated computerized tomography findings were higher (p<0.05). By the univariate analysis outcomes, all research parameters were significantly associated with mortality (p<0.05). Binary logistic regression analy- sis demonstrated that NLR, CRP, and LDH had predictive values for mortality in multivariate analysis (p<0.05). It is prominent that the NLR, CRP, and LDH were discrete from all other parameters and had a high predictive value among the values at the time of admission to the hospital in the study.