Performing a redo-sternotomy when a mammary artery graft is patent can be rather difficult. We previously reported a redo-sternotomy technique involving direct visualization with a retrosternal dissection (DR) method using a Kent's retractor. The DR method in detail is as follows: 1) A midline skin incision is extended to the abdomen about 5 cm. 2) The bilateral costal arches are divided from the rectal muscle. 3). A pair of retractors is placed under the costal arch. 4) A stainless steel wire is applied to the previous sternal wire at the center of the sternum. 5) The retractor and sternal wire are lifted up using the Kent's retractor to widen the retrosternal space. 6) The sternum and sub-sternal tissue are carefully divided using an electronic scalpel or metal retractor with an entirely sternal length. 7) Routine sternotomy is performed using a Stryker. Herein, we report a patient who had undergone cardiac surgery, coronary artery bypass grafting (CABG), using a left internal mammary artery and mitral annuloplasty 2 years previously, and then developed mitral regurgitation caused by infectious endocarditis. He successfully underwent redo-sternotomy and mitral valve replacement using the DR method. In a patient with a patent internal mammary artery, the DR method greatly reduces the risk of graft injury.