We report a case of a distal seeding of invasive thymoma at descending abdominal aortic wall. It is relatively common that direct extension of invasive thymoma into the adjacent great arteries and veins. But distal seeding of invasive thymoma is extremely rare. We found abnormal mass at abdominal aortic wall incidentally during routine transthoracic echocardiography. Operation of aortic segment replacement and mass removal was carried out. Histological evaluation of mass found invasive thymoma.