Thymoma, the most common neoplasm of the anterior mediastinum, is a rare tumor of thymic epithelium that can be locally invasive. We reported 2 cases of invasive thymoma incidentally found during routine coronary artery bypass graft (CABG) surgery at Faghihee Hospital of Shiraz University of Medical Sciences of Iran in a period of about 6 months. The 2 patients were male and above 60 years old. They had no clinical symptoms and radiological evidence of mediastinal mass before detection of the tumor during operation. For both patients mass was completely excised and sent to the laboratory. The ultimate pathological diagnosis of both masses was invasive thymoma (stage 2). There are few reports in which thymomas were found incidentally during cardiac surgery. In spite of rare coincidence, due to being asymptomatic and possibly invasive, special attention to thymus gland during cardiac surgery or other mediastinal surgery and preoperative imaging studies seem to be reasonable approach.