The incidental finding of thymic tumors during thoracic surgery has been reported. Meticulous management planning is necessary if such tumor is found during a cardiac operation. We describe a rare case of asymptomatic invasive malignant thymoma discovered incidentally during routine elective coronary artery bypass grafting in a 48-year-old male. Total thymectomy and enbloc excision of tumor with adjacent involved pericardium, pleura, and phrenic nerve was performed. This was followed by quadruple coronary artery bypass grafting and adjuvant radiotherapy. The patient made an uneventful recovery and remains free from recurrence and angina 2 years following surgery. The different management options available for incidentally occurring malignant thymomas are discussed.