Giant serpentine aneurysms are rare entity, which have unique presentations and distinct angiographic features, with poor prognosis if not treated. In this paper, a patient with a giant serpentine aneurysm originated from right middle cerebral artery was reported. A 38-year-old woman suffered from progressively headache and vision declined. The computed tomography and magnetic resonance image revealed a partially calcified, large mass (approximately 80 × 70 × 60 mm sized) in the right frontal-temple lobe. On computed tomography angiography, an unruptured, giant, partially thrombosed, serpentine aneurysm was confirmed. After treatment by craniotomy, the patient was rehabilitation. Operation is an effective method for the treatment of giant serpentine aneurysms. In addition, cerebral angiography and balloon test occlusion are the crucial way of preoperative assessment.