A 76-year-old woman was admitted with a one-month history of low grade fever and dizziness. She had a palpable right supraclavicular lymph node. Abdominal ultrasonography showed swollen lymph nodes around the abdominal aorta. A specimen from the right supraclavicular lymph node showed malignant lymphoma (diffuse large B cell type). We started chemotherapy according to the low-dose THP-COP protocol (pirarubicin, cyclophosphamide, vincristine and prednisolone) on the 31st hospital day. Since no adverse effects were detected after two low-dose cycles, the patient received a third course with standard doses on the 87th hospital day. The total dose of pirarubicin was 72 mg/m2. Two days after the third course started, she suffered from dyspnea caused by congestive heart failure. A chest X-ray showed advanced cardiomegaly, severe congestion and bilateral pleural effusion. These conditions improved with transvenous administration of diuretics, a vasodilator and phosphodiesterase inhibitor. In this case, congestive heart failure developed even though the total dose of pirarubicin was lower than in previous reports of this complication. When the THP-COP protocol is indicated in elderly patients, cardiotoxicity should be monitored even if the total dose of pirarubicin is very low.