Introduction: Dengue epidemics are known to have occurred over the last three centuries in tropical, subtropical and temperate areas of the world. Dengue creates a huge burden on public health world-wide. Severe dengue can lead to more lethal condition. Hence early recognition of severe cases is important for management of paediatric dengue patients. Objective: To assess the risk factors of severe dengue infection in paediatric patients. Methods: A hospital-based prospective study was conducted at from June 2022 to November 2022 Bangladesh Shishu Hospital & Institute, Dhaka, Bangladesh. Seventy two (72) patients included in the study. In children with high degree clinical suspicion of dengue infection NS 1 antigen (who came within first 72 hours of fever) and/or dengue antibody IgM, IgG (who came after five days of fever) were performed. Positive dengue cases were taken written informed consent & interviewed on the risk factors of dengue infection. Data related to patient’s demography, risk factors, clinical presentation, pattern of dengue infection and outcome were documented on the pre-structured questionnaire. Results: Total of 72 patients with dengue infection met the inclusion criteria, in which 29 and 43 were diagnosed as severe dengue and non-severe dengue infection, respectively. All patients were confirmed by serologic marker (NS-1 or IgM/ IgG Dengue). All subjects were carried out anamnesis, physical examination, and laboratory. Clinical and laboratory examination (complete blood count, AST, ALT, albumin, APTT, S. ferritin and d-dimer) were analysis comparing non-severe dengue and severe dengue patients. Characteristics of 72 research subjects can be seen. On bivariate analysis, there were significant differences of nutritional status, abdominal pain, vomiting, petechiae, hepatomegaly, pleural effusion, leukopenia, thrombocytopenia, hypoalbuminemia, increasing AST > 3x, elevated D- dimer, hyperferritinemia and prolonged APTT between severe and non-severe dengue group. After multivariate analysis, the prognostic factors of severe dengue were overweight/obesity (p=0.003, RR 94), vomiting (p=0.02, RR 13.3), hepatomegaly (p=0.01, RR=69.4), hyperferritinemia (p=0.01, RR=15.4) and prolonged APTT (p=0.005, RR=43.25). In overweight/obesity, vomiting, hepatomegaly, and hyperferritinemia prolonged APTT were prognostic factors in severe dengue infection in children. Conclusion: In conclusion, overweight/obesity, vomiting, hepatomegaly, and hyperferritinemia prolonged APTT were prognostic factors in severe dengue infection in children. Considering these factors for awareness of severe dengue in patients with dengue virus infection. Clinicians should emphasize the monitoring of these factors for early detection of serious dengue state.