Acute lymphoblastic leukemia rarely manifests with pericardial and pleural effusion as an initial presentation of the disease. It is imperative to diagnose these type of cases promptly and accurately in order to start timely therapy. We present a case of a 27–year–old–male who presented to the emergency department with severe respiratory distress. Chest X–ray and CT thorax showed massive pericardial and bilateral mild pleural effusion. Cytological examination of the pericardial fluid led to the diagnosis of underlying acute lymphoblastic leukemia. Further, hemogram, bone marrow aspirate, and flow cytometry analysis confirmed the diagnosis of T–lineage acute lymphoblastic leukemia. The patient responded dramatically to the induction chemotherapy with the complete resolution of the pericardial and pleural effusion. The patient is on follow up at present and doing well. This case highlights the importance of the early diagnosis of acute leukemia by cytopathological analysis of body cavity fluids.