Serous effusions may occur as complications in different types of lymphomas. Among these, pleural effusions are commonly observed; however, involvement of peritoneal or pericardial cavity is rare. Different diagnostic modalities like cytological examination, immunocytochemistry, cytogenetics have been used to diagnose various malignancy, thereby attaining a fast and accurate diagnosis. As effusion in lymphoma is associated with poor outcome, an early diagnosis is very much important. We describe a case of aggressive Non-Hodgkin lymphoma, i.e., Burkitt lymphoma in a previously healthy 7-year-old male child, where the diagnostic ascitic & pleural fluid cytomorphology in conjunction with flow-cytometric immuno-phenotypic analysis of the effusion helped in clinching an early diagnosis.