Introduction- Dengue is regarded as the most important arthropod-borne viral infection in humans and is the second most important re-emerging tropical disease. Dengue infections are increasing resulting in more illness and death and in 2012 World Health Organization (WHO) reclassified dengue as the most important mosquito-borne viral disease in the world. Given the heterogeneous nature of the clinical presentation of dengue, identifying robust and sensitive clinical or laboratory predictors of dengue fever and its severity has not been an easy task. Neutrophil-to-lymphocyte ratio (NLR) can be easily calculated based on a complete blood count by dividing the Neutrophil percentage by Lymphocyte percentage. There is enough literature to suggest that NLR has prognostic significance in various diseases. However, no studies have focussed on NLR as a prognostic marker for dengue. Aim- To study NLR in dengue patients and assess its role in relation with age, gender,serological tests for dengue and platelet count. Materials and Methods- This retrospective observational study was carried out at Tertiary care hospital in Northwest Maharashtra. 100 diagnosed and admitted cases of dengue were included in this study. Clinical data and laboratory data were reviewed and analysed. Chi Square test was done and its significance noted. Results- In our study, Ns1Ag dengue serology test was found to be more common in males indicating recent infection and Ns1Ag, IgM and IgG more common in females indicating recent and past infection. NLR < 2 strongly correlates with low platelets indicating severity of disease and reversal of NLR > 2 correlates with improvement of disease. NLR < 2 was more common in 0-20 years age group, younger the age lesser the NLR and hence more severe the disease. Conclusion- From our study we found that there is a significant relation between NLR to the severity of dengue fever in adult patients and by keeping an eye on the NLR we can predict the prognosis and the severity of the disease in patient. Lower the NLR ratio severe the disease. Hence NLR can be used as a prognostic indicator in dengue patients.