Cerebrospinal fluid leakage following meningomyelocele surgery is a frequent complication in the wound healing period and is associated with wound dehiscence. CSF loss can cause severe hyponatremia, especially in the newborn and early infancy periods when dietary sodium content is relatively low. Hyponatremia in the newborn period can result in adverse neurodevelopmental outcomes. In addition, hyponatremia's cerebral effects can increase complications in neurosurgery patients. The authors present the case of a newborn in whom CSF leakage from the operative site and severe hyponatremia developed following meningomyelocele surgery. To the best of their knowledge, severe hyponatremia caused by CSF leakage after meningomyelocele surgery has not been previously reported in the literature.