Deep sternal wound infections are potentially life-threatening complications after cardiac operations because they can spread into the mediastinum and cause postoperative morbidity and mortality. We present a 65-year-old man with a history of coronary artery bypass grafting. A large sternal defect was left after debridement. After brief vacuum-assisted closure (VAC), a free myocutaneous flap of the anterolateral thigh (ALT) was used to fill the dead space. At the 9-month follow-up, the wound had healed completely without tissue loss or complications, and the patient returned to normal life. This was a successful treatment of a deep sternal wound with free flap coverage.