Introduction: The present study aimed to compare the haematological and biochemical indices between Dengue patients, and assess the relationship of these indices inprognosis and severity of Dengue fever. Materials and Methods: A total number of 40 children with confirmed diagnosis of Dengue fever who visited and some of them were admitted Sri SathyaSai Medical College and Research Institute in Chennai were selected in this case-control study. Haematological, biochemical and neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), and outcome of the disease were assessed in this study. Results: The number of children confirmed diagnosed with Dengue fever were 40, they were further divided into three different group based on severity of the disease. Haematological and biochemical variables were statistically significant in these three different groups. Neutrophil count, platelet count, lymphocyte count, and haemoglobin concentration were also higher in the dengue fever with warning signs patient group (P=0.001). NLR and PLR were significantly higher in severedengue patients compared to the mild patients (P=0.01). NLR had a significant relationship with the severity of the disease. Multivariable analysis for diagnostic values of NLR and PLR showed that the NLR and PLR were significant at 2.336 (95% CI: 1.636–3.336) and 1.4 (95% CI: 0.28-0.29), respectively. Conclusion:Platelet-to-Lymphocyte Ratio (PLR) and Neutrophil-To-Lymphocyte Ratio (NLR) can be used as a prognostic marker for Dengue disease given the significant difference of PLR and NLR between mild Dengue patients and severe Dengue patients.