A 69-year-old woman was referred to our hospital for investigation of an abnormality detected by a chest roentgenogram, and was subsequently found to have an ascending aortic aneurysm. She had not suffered any symptoms such as headache or polymyalgia rheumatica. Aneurysmectomy and reconstruction of the ascending aorta was performed using cardiopulmonary bypass, and pathological examination of the aneurysmal wall revealed giant cell arteritis (GCA). Preoperatively, she had not suffered any temporal pain, and no signs of inflammation were detected serologically. GCA is a rare cause of aortic aneurysm in the Japanese population, and a brief review of the literature on this unusual entity is presented following this case report.