A giant serpentine aneurysm (GSA) in the anterior cerebral artery (ACA) poses a technical challenge in treatment given its large size, unique neck, and dependent distal vessels. Here we report the case of a GSA in the ACA successfully treated with a combined surgical and endovascular approach. A 54-year-old woman presented with dull headache. On brain computed tomography (CT), a large mass (7 cm × 5 cm × 5 cm) was identified in the left frontal lobe. Cerebral angiography revealed a GSA in the left ACA. Bypass surgery of the distal ACA was performed, followed byocclusion of the entry channel via an endovascular approach. Follow-up CT performed 5 days after treatment revealed disappearance of the vascular channel and peripheral rim enhancement. Follow-up imaging studies performed 7 months after treatment revealed gradual reduction of the mass effect and patency of bypass flow. No complications were noted over a period of 1 year after surgery.