A delayed pericardial effusion developed in a recipient of a cardioverter defibrillator (ICD). After an uneventful implant procedure and postoperative recovery, the patient suffered loss of appetite and fatigue, and was re-admitted to the hospital 48 days later. Her vital signs were stable and cardiac silhouette on chest roentgenogram was normal. However, blood cell counts and chemistry revealed the presence of anemia and liver dysfunction, an echocardiogram showed a diffuse pericardial effusion, and computed tomography suggested that the ICD lead, screwed in the right ventricular outflow tract, had perforated the wall. In order to make a prompt diagnosis and initiate timely corrective treatment, the physician in charge of long-term follow-up should remember that a pericardial effusion can be delayed and accumulate in the absence of typical signs of cardiac tamponade after ICD lead implantation.