We report a case of malignant pericardial effusion due to breast cancer that was successfully controlled by intrapericardial chemotherapy using pirarubicin. A 53-year-old woman underwent breast conserving therapy for left breast cancer in 1996. She was given CAF therapy and UFT as adjuvant therapy. Three years and 10 months after operation, she had malignant pericardial and pleural effusion. Pericardiocentesis and pleurocentesis were performed immediately. Pericardial effusion relapsed after some time and she was treated with intrapericardial chemotherapy using pirarubicin. After this treatment she has not suffered from pericardial effusion for 1 year and 4 months to date. This case suggests that intrapericardial chemotherapy is effective for malignant pericardial effusion.