We report successful treatment of mediastinitis with rerouting of the outflow vascular prosthesis after bi-ventricular assist device (Bi-VAD) implantation. A 23 years-old male with fulminant myocarditis underwent VAD implantation. He required sternotomy three times. Mediastinitis developed after the third surgery, and negative pressure wound therapy (NPWT) with irrigation was applied. The infection was well controlled, but after 3 months of NPWT hemorrhage developed because of injury of the outflow vascular prosthesis in the anterior mediastinum. We rerouted the outflow vascular prosthesis to the descending aorta via the left thoracic cavity. After rerouting, artificial material was removed from the anterior mediastinum. The sternal wound healed completely after NPWT. Intractable mediastinitis after extra-corporeal VAD implantation may be treated with irrigation and NPWT, but there is a possibility of outflow graft injury. A sternal wound could be closed as a secondary healing process by rerouting the outflow vascular prosthesis.