A case of 53-year-old female with unstable angina pectoris and primary right breast cancer is presented. Simultaneous operation including coronary artery bypass grafting and modified radical mastectomy was performed. On the beating heart coronary anastomoses were done without cardiopulmonary bypass (CPB) through median sternotomy (OPCABG). Immediately after OPCABG cancer operation was performed under stable hemodynamics without any bleeding tendency. There were neither perioperative nor postoperative complications noticed. Three months after operation adjuvant local radiotherapy was started. Concomitant surgical treatment seems to be safe and beneficial in carefully selected patients who have surgically correctable coronary artery disease and potentially curable breast cancer.