In this report, we describe the cases of four patients with advanced thymic malignancy who developed tumor-related cardiac tamponade. Two patients had thymic carcinoma; the other two had thymoma. All patients underwent pericardiocentesis and drainage of pericardial effusion, combined with the administration of intrapericardial carboplatin (CBDCA). Although primary or disseminated tumors were located near the pericardium, tumor cells were not detected in the pericardial effusion. Additionally, symptoms of cardiac tamponade disappeared after drainage was performed, and no major complications were observed with respect to intrapericardial administration of CBDCA. All patients received further therapy for their malignancies. Post-therapy survival for all four patients was good: 98 and 414 days for the two patients with thymic carcinoma and 626 and 1,632 days for the two patients with thymoma.