The patient was a 36-year-old female who had undergone Auchincloss operation for left breast cancer at another hospital when 29 years old. Three years ago she was transferred from another hospital to our department complaining of dyspnea. Under the diagnosis of cardiac tamponade, we treated her with pericardial drainage and systemic chemotherapy (intravenous dosage of trastuzumab and vinorelbine: VNR), and then pericardial effusion disappeared. Further medical treatment was continued on an outpatient basis. One year later, cardiac tamponade developed again. We performed echo-guided pericardiocentesis and removed 600 mL of bloody effusion. The cytology of the effusion showed class V. Pericardial effusion recurred, so we instilled OK-432 and mitomycin C (MMC) twice. After that the cytology diagnosis became negative, and the heart shadow in chest X-P reduced. The pericardial effusion has never occurred until now. We also gave her systemic chemotherapy (intravenous dosage of trastuzumab)and endocrine therapy (peroral administration of medroxyprogesterone acetate). She made a remarkable recovery with these treatments and could go back to work.