Background: Dengue fever is a major arboviral infection in tropical and subtropical regions, and derangement of haematological parameters is central to its clinical course and prognosis. 
Objective: To evaluate the pattern of haematological parameters in serologically confirmed dengue patients and to assess their relationship with disease severity. Methods: A hospital-based descriptive study was conducted on 180 confirmed dengue patients over a six-month period. Complete blood counts were analysed using an automated haematology analyser, and parameters were correlated with the presence of warning signs. 
Results: The mean age was 28.6 ± 13.2 years with a male predominance (61.1%). Thrombocytopenia was the most frequent abnormality (78.3%), followed by leukopenia (47.8%) and atypical lymphocytes (37.8%). The mean platelet count fell to a nadir of 65 ×10³/µL around the sixth day of illness. Severe thrombocytopenia (<50 ×10³/µL) and raised haematocrit were significantly associated with warning signs (p < 0.05). 
Conclusion: Serial monitoring of platelet count and haematocrit provides a simple, cost-effective tool for early risk stratification and timely management of dengue fever.