Extrinsic left atrial compression is an uncommon source of hemodynamic compromise that can be caused by many mediastinal structures including bronchogenic cysts, carcinoma, lymphoma, thymoma, aortic aneurysm and diaphragmatic hernia. We describe an unusual case of a 26-year-old man presenting with symptoms of left heart failure. Transthoracic echocardiography demonstrated extrinsic left atrial compression caused by a metastatic testis non-seminomatous germ cell tumor. Compression of the left atrium caused impaired left atrial filling, leading to pulmonary venous hypertension and pulmonary edema. To our knowledge, the present case is the first reported case of mediastinal metastatic testis non-seminomatous germ cell tumor causing symptoms of left heart failure by externally compressing the left atrium.