Background: The severity of COVID-19 could be evaluated by examining several blood parameters mainly white blood cell (WBC) count, granulocytes, platelet, and novel hemocytometric markers neutrophil to lymphocyte ratio (NLR), platelet-to- lymphocyte (PLR), and lymphocyte to monocyte ratio (LMR). Aim: The current study was conducted to investigate alteration in blood parameters and their association with the severity and mortality of COVID-19 patients. Material and Method: This retrospective cross-sectional study was conducted in the Department of pathology, in a tertiary care centre, India. A total of 300 RT-PCR COVID-19 positive patients of age group between 18-80 years were enrolled in our study. The hematological parameters were compared between different grades of severity. The following parameters were assessed: hemoglobin, platelets count, total leukocyte counts (TLC), relative neutrophil count, relative lymphocyte count, neutrophil-to-lymphocyte ratio (NLR), and absolute eosinophil counts (AEC). Results: The overall mean age observed in our study was 52.35 years, majority of the patients were male (57.6%). Associated co morbidities found in 83.6% of cases. Our results showed that COVID-19 survivors exhibited lower hemoglobin (Hb) and hematocrit (HCT), while showed higher Red Cell Distribution Width (RDW), neutrophil lymphocyte ratio (NLR), and lymphocytes. Logistic regression analysis showed that age greater than 40 years old, neutrophilia and high NLR were associated with more deaths. Conclusion: Routine hematological parameters are cost-effective and fast predictive markers for severe COVID-19 patients, especially in resource-constrained health care settings to utilize limited ICU resources more effectively.