Hydatid disease is a zoonosis caused by Echinococcus granulosus. It is seen most frequently in the liver and lungs in adults. The mediastinal location of this disease is rare. Herein, we report the case of a 38-year-old male with signs of heart failure related to a rupture of a mediastinal hydatid cyst with pericardial tamponade. The diagnosis was confirmed by echocardiography, computed tomography, and hydatic serology, and the patient was operated and put on albendazole for 3 months with favorable clinical course.