Introduction: Incidence of dengue infection has increased around the world in recent decades and has become a major international public health concern. Early diagnosis is essential and clinical suspicion is based on the frequency of symptoms in the population. The exact clinical profile is important for management and prognosis. Objective: This study is an attempt to describe the Clinical Characteristics & Observation of Hospitalized Cases of Dengue Fever: A Study in Tertiary Care Hospital, Dhaka, Bangladesh. Materials and Methods: A hospital-based prospective study was undertaken in the Paediatrics Dept. in Tertiary Care Hospital, Dhaka, Bangladesh (July -October 2018). NS1 antigen and IgM dengue antibody-positive cases were included. These patients were admitted with fever, myalgia, headache, vomiting, abdominal pain or bleeding manifestations. NS1 antigen and IgM dengue antibody was estimated using capture ELISA. The diagnosis of dengue fever, dengue hemorrhagic fever and dengue shock syndrome was based on the WHO (World Health Organization) criteria. Results: The study enrolled 101 patients of suspected dengue fever of whom 51 (50.49%) were serologically confirmed to have dengue infection. 28 (55.0%) patients were males and 23 (45.0%) were females. 38 (37.62%) patients had classic dengue fever while 12 (11.88%) fulfilled the criteria of dengue hemorrhagic fever. Of those patients with dengue hemorrhagic fever, 6 patients had developed dengue shock syndrome. Conclusion: Dengue presents as a highly unspecific illness and is hardly recognized as a clinical entity by primary health care physicians. Dengue infection can have potentially fatal consequences, and to date, vector control methods to prevent the spread of the virus have been unsuccessful. Although there are promising vaccine candidates in development, further studies are required for a greater understanding of the humoral immune responses to Dengue infection and observation disease pathogenesis.