Intracavitary metastasis causing right ventricular outflow tract (RVOT) obstruction is very rare. Combination of cardiac tamponade with RVOT obstruction due to intracavitary metastasis has never been reported in the literature. Herein, we report a case of colonic carcinoma with sudden onset of severe dyspnea. Echocardiography detected cardiac tamponade as well as a huge intracavitary mass obstructing the RVOT. Pericardiocentesis and surgical resection of the right ventricular mass were performed but the patient died during operation. Thus, the combination of intracavitary RVOT obstruction and cardiac tamponade in a patient with carcinoma suggests extensive myocardial and pericardial involvement with a poor prognosis.