A 40-year-old female presented with growth hormone (GH)-secreting pituitary adenoma associated with primary moyamoya disease manifesting as amenorrhea, acromegaly, and transient ischemic attack. Magnetic resonance (MR) imaging revealed a tumor mass extending from the sella turcica to the suprasellar cistern, and MR angiography demonstrated stenoses in the bilateral internal carotid arteries with basal moyamoya vessels. Her blood GH and insulin-like growth factor (IGF-1) levels were elevated to 78.94 and 923.0 ng/ml, respectively. The patient underwent removal of the pituitary adenoma because her ischemic symptoms disappeared after oral aspirin medication. Subtotal resection resulted in persistence of the high blood GH and IGF-1 levels. Postoperative MR angiography showed progression of the stenoses in the bilateral internal carotid arteries. Excess systemic GH and IGF-1 may participate in the progression of vascular disease and so could have caused the deterioration of the moyamoya disease.