We report a 51-year-old man who was diagnosed with concomitant coronary artery disease and systemic lupus erythematosus (SLE). He required urgent coronary artery bypass grafting (CABG) before the initiation of steroid therapy. Steroid therapy was initiated on postoperative day 2 due to the aggravation of SLE. However, he displayed persistent infection and fever, and the steroid dose was gradually decreased, resulting in the worsening of SLE by postoperative day 21. We closely monitored his infection status and renal function and regulated the steroid dose accordingly. The patient stabilized and was discharged on postoperative day 60 without further complication. Meticulous post-operative management is required in acute SLE patients who need open heart surgery.