Aim: Now a days, majority of dengue patients with an abnormal aspartate aminotransferase (AST) level, and a decreased blood platelet count (PLT) is linked to the severity of dengue fever.Hence, we aimed to assess the diagnostic value of Aspartate Aminotransferase / Platelet Count Ratio Index (APRI) for predicting dengue severity.Methods:A prospective study done among 115 patients with confirmed dengue fever (ELISA based NS1 antigen/igmantibody positive report) who were admitted in tertiary care hospital from June 2021 to December 2021. All patients were clinically assessed and investigated for lab parameters on day 1, day 4 and day 7 or onthe day of discharge/death. Data was analysed using SPSS version 21.Findings: A total of 115 patients, 76 (66.1%) males and 39 (33.9%) females, with the median age of the patients was 27 year (range from 15-45). Most of the patients (65, 56.5%) had dengue fever without warning signs and 20 patients (17.4%) had severe dengue disease. The aspartate aminotransferase (AST), leukocyte count, platelet count (PLT), aspartate aminotransferase/platelet count ratio index (APRI) showed a significant association with severe dengue (p<0.05). With the observed 2.5 cut off value, we found the sensitivity and specificity of APRI for prediction of dengue severity as 80.0% and 76.8% respectively.Conclusion: Our study revealed that Aspartate aminotransferase/platelet count ratio index (APRI), can be useful for clinicians to predict the severity of dengue fever infection during the onset of symptoms and course of treatment for better outcome.