A 24-year-old woman with a multilocular sacciform aneurysm in a right-sided aortic arch was successfully treated by aneurysmorrhaphy. Although the cause of the aneurysm could be attributed to congenital factors, its growth was considered to be related to the features of the right-sided aortic arch; strong haemodynamic forces were caused by sharp curving of the aorta which started from an unusually high position and subsequently had a decreased radius.