A 24-year-old woman developed subarachnoid hemorrhage and left frontal lobe ischemia following uneventful right transconjunctival orbital decompression for thyroid-related immune orbitopathy. CT, MRI, CT angiography, and carotid angiography confirmed subarachnoid hemorrhage and brain ischemia on the left side without any cerebral vascular abnormalities on either side. All tests were unremarkable. She fully recovered at last follow-up, 4 months after surgery. We did not find any reason for the subarachnoid hemorrhage and left frontal lobe ischemia. This complication should be considered after orbital surgery for patients with thyroid-related immune orbitopathy.