Pyoderma gangrenosum (PG) is an ulceronecrotizing dermatosis that can occur after minor trauma or surgery and is rare after cardiac surgery. We report a case of PG after coronary artery bypass grafting (CABG) in a patient with chronic idiopathic myelofibrosis (CIMF). Diagnosis was made with punch skin biopsy and he was treated with systemic steroids. His lesions showed remarkable improvement with this therapy. Cardiothoracic surgeons need to consider this diagnosis in all rapidly expanding postoperative lesions, especially those that do not improve with debridement or antibiotics or conservative wound care.