Primary cardiac lymphoma (PCL) is an extremely rare malignancy and an uncommon presentation of Non-Hodgkin’s Lymphoma. We report the first case of Precursor B-cell lymphoblastic PCL. A 44 year old Caucasian woman presented to our institution with one week history of worsening dyspnea, leg swelling and a weight gain of 12 pounds. Urgent echocardiography revealed pericardial effusion with tamponade physiology. Subsequent imaging showed a mass in the right atrio-ventricular groove. Pericardiocentesis was performed and cytopathology showed malignant appearing immature lymphocytes. Immunophenotypic analysis revealed 85% of the cells to be CD19 and CD10 positive. The cells were negative for CD20, surface light chains, CD3 and CD5 consistent with immature B-cells.