A 35-year-old female presented with moyamoya disease coincidentally associated with a persistent primitive trigeminal artery (PPTA). Bilateral encephalo-duro-arterio-synangiosis was performed and the postoperative course was uneventful. Moyamoya disease and PPTA might have a congenital origin, but moyamoya disease may be promoted by a PPTA. The hemodynamics of PPTA during progressive occlusive change in the internal carotid artery in moyamoya disease should be re-evaluated to determine its function in the development of moyamoya vessels.