Pericardial disease is a common complication of solid tumors and occasionally seen in hematologic malignancies. Pericardial effusion, when it occurs, is usually caused by tumor seeding of the pericardium leading to a serous effusion or by mass effect from mediastinal lymphadenopathy blocking drainage of lymphatic ducts. Pericardial disease from non-Hodgkin's lymphoma is uncommon and malignant pericardial effusion is even rarer. Here we present a case of a 31-year-old male with diffuse large B-cell lymphoma who developed cardiac tamponade from a malignant pericardial effusion.