Introduction : Although there are various diagnostic tools like computed tomography, magnetic resonance imaging, and positron emission tomography, it is sometimes difficult to precisely diagnose cardiac tumors. Early pathological diagnosis is crucial for possible chemotherapy and/or radiation therapy in cardiac malignant lymphoma. Objectives : To assess the diagnostic value of pericardial excisional biopsy and cytology of pericardial effusion for the pathological diagnosis of cardiac lymphoma. Methods : Five patients had a clinical diagnosis of cardiac tumor with no pathological diagnosis. The pericardial biopsy and pericardial effusion were obtained without sternotomy through the subxyphoid by a small incision under local anesthesia. Results : All procedures were completed without complications. In 3 cases, the cytology of pericardial effusion yielded a diagnosis of malignant lymphoma. One patient who had a negative cytology result in whom surgical resection was performed for definitive diagnosis and tumor volume reduction was found to have malignant lymphoma. The remaining patient underwent tumor biopsy via a cardiac catheter and benign lymphoma was diagnosed. There were no specific findings in the pericardial excisional biopsy in 3 cases. Conclusion : The analysis of cytology of pericardial effusion obtained through the subxyphoid may be useful for the diagnosis of cardiac malignant lymphoma. Pericardial excisional biopsy may not be necessary for the diagnosis of cardiac malignant lymphoma.