A 69-year-old woman presented with a transethmoidal meningoencephalocele manifesting as gradually developing anosmia. Examinations revealed a mass in the nasal cavity associated with multiple angiomas in her lip and orbit. Neuroimaging showed meningoencephalocele extending via the ethmoid sinus to the nasal cavity. She had no history of craniofacial trauma and intranasal or intracranial operation, and no skull base tumor was detected. Frontal base reconstruction was performed with a two-layer vascularized flap to prevent cerebrospinal fluid leakage. The dural defect was repaired with the pericranial flap, and the bony defect of the cribriform plate was reconstructed using the reversed U-shaped split temporalis musculofascial flap. Transethmoidal meningoencephalocele is a rare congenital malformation and almost half of the cases are identified in the first year of life. We should be aware of this clinical pathology and avoid unexpected rhinorrhea in elderly patients. The most important aspect of the operation is watertight closure of the patent passage to the intracranial compartment. The reversed U-shaped split temporalis musculofascial flap is useful to reconstruct the midline frontal base defect.