Metastatic cardiac tumors are commonly detected during autopsy. However, they are seldom diagnosed during life, and surgical resection is rarely indicated. Among the malignant tumors, colon cancer rarely metastasizes to the heart. We report a case of a 70-year-old woman with sigmoid colon cancer, which metastasized to her heart and caused obstruction of the right ventricular outflow tract. The tumor had already metastasized to the liver, lungs, periaortic lymph nodes, and peritoneum. Cardiopulmonary bypass surgery was performed to excise the right ventricular metastatic tumor and to reconstruct the tricuspid valve. Histological analysis of the specimen confirmed a metastatic adenocarcinoma. Although this surgery was performed as palliative cancer therapy, the patient's symptoms were satisfactorily improved. Follow-up echocardiography 2 months after her cardiac surgery showed no space-occupying mass in the right ventricle.