Background: Dengue fever is caused by dengue virus which is a mosquito borne pathogen and this disease is now endemic in India. This infection produces varied haematological changes in the patient which can at times be life threatening. The aim of this study was to identify these changes in serologically confirmed dengue cases. Methods: 50 cases diagnosed as dengue based on NS1 antigen were analysed for haematological parameters which included haematocrit value , total leucocyte count, differential leucocyte count, platelet count and peripheral blood smear. Results: Common haematological abnormalities detected were leucopenia, raised haematocrit, thrombocytopenia and presence of activated lymphocytes. Conclusion: Hematological parameters play a key role in early diagnosis of dengue infection. Monitoring these parameters aids in effective management of patients and prevention of complications.