There are more than a few risks of hemorrhage complication in patients with amyloidosis. Although most cases with amyloidosis exhibit minor bleeding manifestations, they can be occasionally associated with life-threatening problems. To our knowledge, there are only a few cases of spontaneous pericardial hematoma associated with amyloidosis. We here report a patient who suddenly died of cardiac tamponade with massive pericardial hematoma 7 years after the diagnosis of familial amyloid polyneuropathy (FAP). A 69-year-old female with FAP with cardiogenic shock was admitted to our emergency room. Although she previously underwent permanent pacemaker implantation for atrial fibrillation with slow ventricular response, electrocardiogram showed a critical pacing failure. Emergent telemetry check revealed a sudden extreme increase of pacing capture threshold in the right ventricle. Maximum pacing voltage could not improve the critical condition, and she died 7 h after arrival. Autopsy showed a massive pericardial hematoma in the right ventricular free wall, and microscopic examination revealed typical amyloid deposition in the arterial wall of the pericardium. In this case, it is assumed that a sudden rupture of fragile pericardial vessels with amyloid deposition led to the lethal pericardial hematoma.