Ischemic complications can occur after revascularization surgery for moyamoya disease, but acute contralateral internal carotid artery (ICA) occlusion is an extremely rare complication. The patient was a 51-year-old woman with no medical history. Left frontal lobe infarction and bilateral ICA terminal stenosis were identified by repeated transient right paresis and aphasia. We diagnosed her with quasi-moyamoya disease associated with hyperthyroidism and performed revascularization surgery for the symptomatic left side. Although neurological symptoms did not worsen immediately after the surgery, disturbance of consciousness, right conjugate deviation, and left paresis appeared 4 hr after the surgery. New infarction appeared in the right frontal lobe, and the blood signal beyond the right middle cerebral artery (MCA) disappeared on MRI and MRA. Mechanical thrombectomy (MT) using a suction catheter improved antegrade blood flow in the MCA. The left paresis remained at discharge (modified Rankin Scale score = 4), but she was able to walk independently 3 months after the operation and was independent at home. Acute contralateral ICA occlusion after revascularization for moyamoya disease is an extremely rare complication, but the symptoms can be severe and treatment should be considered. To the best of our knowledge, there have been no reports of MT for postoperative acute contralateral ICA occlusion. Since the results of endovascular treatment such as percutaneous transluminal angioplasty and stent placement for patients with moyamoya disease are poor, MT using an aspiration catheter could be a good treatment option.