We report a unique case of an anterior cerebral artery aneurysm in a patient with embryonic unfused middle cerebral artery anomaly. The arterial twigs of the middle cerebral artery supply the entire middle cerebral artery territory including the lenticulostriate branches. There was a vessel incorporated into the aneurysm, which was referred to as an accessory middle cerebral artery and it gave rise to a lenticulostriate branch. The aneurysm was occluded with detachable coils using a remodeling technique. After successful occlusion of the aneurysm the so-called accessory middle cerebral artery including its lenticulostriate branch started to fill from the anomalous middle cerebral artery network and the patient did not experience any ischemic injury.