Carotid artery aneurysm secondary to cystic medial necrosis is a rare clinical entity. We report a 59-year-old Chinese male patient who presented with a pulsatile right neck swelling for 2 months. Partial resection of the aneurysm with primary anastomosis of the internal carotid artery was performed. Histopathological examination of the aneurysmal wall demonstrated cystic degeneration of the media with accumulation of glycosaminoglycan material, consistent with the features of cystic medial necrosis. The pathogenesis of carotid artery aneurysm secondary to cystic medial necrosis is discussed.