Background: Dengue is an acute febrile illness transmitted by Aedes aegypti mosquito. An early diagnosis based on clinical features and treatment reduces complications and mortality. Objectives: To assess the clinical features of dengue fever patients along with changes in haematological and biochemical parameters. Methodology: Tertiary hospital based observational test study during June 2016 to May 2017 where 300 patients above 18 years of age with Dengue fever were included. Results: Haematological and biochemical abnormalities included thrombocytopenia (73.3% cases), raised hematocrit (32% cases), elevated liver enzymes (70.7% cases). Ultrasonography showed gall bladder sludge (31% cases), Acalculous Cholecystitis (31% cases), Ascites (19% cases). Conclusion: Clinical features and basic haematological and biochemical parametres lead to early diagnosis of dengue fever without waiting for dengue serology.