Extensive research has been conducted to identify the predictive criteria for COVID-19 disease. White blood cell, C-reactive protein, CRP/albumin ratio, neutrophil-to-lymphocyte ratio and ferritin are among the indicators of increased inflammatory response; hence, they could be used to determine the prognosis of COVID-19 cases. Within the scope of this study, we aimed to elucidate the predictivity of NLR, CAR and other laboratory parameters on the duration of hospital stay and mortality in patients with COVID-19. Materials and Method:The data of 1516 COVID-19 patients who were hospitalized in our institution have been analyzed retrospectively. Patients were divided into two groups those who deceased within the first 10 days of hospitalization (Group I, ≤10 days) and those who deceased in the later period (Group II, >10 days). Age, gender, time to mortality after hospitalization, neutrophil count, CRP, neutrophil-to-lymphocyte ratio (NLR), CRP/albumin ratio (CAR), and D-dimer values were obtained from blood samples taken during hospitalization. Results: NLR and CAR values were significantly higher in those who died in the first 10 days compared to the other group (p<0.02 and p<0.001, respectively). In addition, WBC, neutrophil, CRP and D-dimer levels were statistically significantly higher than the other group (p<0.05). Logistic regression analysis results for NLR and CAR were significant. The cut-off values were calculated (5.74 and 4.27, respectively) for both parameters. Among the most common comorbid diseases were hypertension (HT) in 41%, coronary artery disease (CAD) in 41.7%, asthma-chronic obstructive pulmonary disease (COPD) in 36.7%, diabetes mellitus (DM) in 36.1%. Conclusion: NLR and CAR may have a decisive influence in determining the length of stay in hospital for patients who die in hospital due to COVID-19. In addition, it is recommended that COVID-19 cases with diabetes be followed closely.