Thirst is stimulated by increases in effective plasma osmolality that are detected by cerebral osmoreceptors located in the vascular organ of the lamina terminalis. However, surgical destruction or organic lesions of the lamina terminalis decrease the sensation of thirst in response to increased plasma osmolality. A 17-year-old boy who was diagnosed with craniopharyngioma at the age of 10 years and underwent tumor resection and gamma knife surgery was admitted for non-symptomatic severe hypernatremia. Although the sodium level was 173 mmol/L and serum osmolality was also high (371 mOsm/kg), the patient did not report increased thirst. Laboratory analysis revealed hypertonic dehydration and acute non-oliguric renal failure due to dehydration. Treatment was based on correction of hypernatremia with hydration and education about regular, periodic water ingestion. The patient's hypernatremia and acute non-oliguric renal failure resolved with controlled daily fluid intake. To our knowledge, this is the first report of decreased thirst sensation secondary to craniopharyngioma and tumor resection leading to severe hypernatremia and non-oliguric renal failure in an adolescent.