Hypovolemic hyponatremia in the pediatric population is a common electrolyte disturbance, most often secondary to salt loss in excess of water loss from the gastrointestinal tract (e.g., diarrhea). We present an unusual case of an 18-month-old boy who had recurrent hyponatremic, hyperkalemic dehydration secondary to salt losses from cerebrospinal fluid rhinorrhea and low dietary salt intake. An extensive evaluation revealed normal renal and endocrine function. Head imaging revealed a persistent craniopharyngeal canal, suggesting a communication between the nasopharynx and subarachnoid space. The nasal secretion was confirmed to be cerebrospinal fluid by detection of beta transferrin-2. This case highlights cerebrospinal fluid rhinorrhea as an unusual, but clinically significant, cause of sodium loss.