A rare case of fenestration of the intracranial internal carotid artery (ICA) was identified by angiography in a 51-year-old female with suspected subarachnoid hemorrhage. Only two similar cases have been reported previously. Fenestration tends to develop on the right side and near the bifurcation of the ophthalmic artery. Congenital factors at the 4 mm embryonic stage may be involved in the fenestration of the intracranial ICA.