Background: Dengue fever is a significant global health concern, particularly in tropical and subtropical regions, including Bangladesh. Hematocrit levels play a crucial role in monitoring plasma leakage and disease severity in Dengue patients. This study aims to observe the hematocrit levels and other hematological parameters among Dengue fever patients admitted to a tertiary care hospital. Methods: This cross-sectional observational study was conducted at Tairunnessa Memorial Medical College Hospital from March 2022 to August 2022. A total of 80 confirmed Dengue patients were included in the study. Daily hematocrit levels, hemoglobin levels, and white blood cell counts were recorded over a 10-day monitoring period. Data analysis included descriptive statistics to assess trends and variations in these hematological parameters. Result: The majority of participants (27.5%) belonged to the 18-27 years age group, with a nearly equal gender distribution (52.5% males, 47.5% females). Dengue fever with and without warning signs accounted for 93.75% of cases, while severe Dengue was observed in only 6-25% of cases. Fever was present in all patients, with headache (65%) and myalgia (47.5%) being the most common associated symptoms. The mean hematocrit level peaked on Day 3 (47.58±5.22%) before progressively declining, while hemoglobin levels followed a similar trend, peaking on Day 3 (16.02±1.92 g/dL) and reaching the lowest on Day 9 (12.82±1.42 g/dL). White blood cell counts declined until Day 4 (3333.52±24.11 per cu.mm) and then showed a gradual increase. Recovery was observed in 93.75% of cases, with a mortality rate of 1.25%. Conclusion: The study highlights the importance of monitoring hematocrit and other hematological parameters in Dengue fever patients for early detection of complications and effective management. While the majority of cases were Dengue fever with and without warning signs; the observed hematological trends underscore the need for vigilant monitoring to prevent severe outcomes. Further large-scale studies are warranted to strengthen clinical guidelines for Dengue management.