We report a surgical case of prosthetic valve obstruction after mitral valve replacement by a St. Jude Medical valve. A 66-year-old woman was admitted because of congestive heart failure. Prosthetic valve obstruction was diagnosed by transthoracic echocardiography and cine-fluoroscopy. Re-do cardiac surgery was indicated after a week of heparinization. Circumferential pannus formation into the orifice beyond the pivot guard of the prosthesis on the atrial side and one piece of the leaflet was covered with a fibrous overgrowth on the atrial side. We concluded that once the diagnosis of valve thrombosis is established, urgent operation is preferred in patients with hemodynamic instability before the development of cardiogenic shock or multiple organ failure.