Adipsia is a rare disorder that occurs due to damage to the osmoreceptor and not feeling thirst despite hyperosmolality. Adipsic hypernatremia can occur when there is damage to the anterior communicating artery that supplies blood to osmoreceptors, and the level of arginine vasopressin secretion varies widely. A 37-year-old woman, suffering from severe headache, was consulted to the nephrology department for hypernatremia and polyuria after clipping of a ruptured aneurysm in the anterior communicating artery. Despite her hypernatremic hyperosmolar state, she denied thirst and did not drink spontaneously. She was diagnosed adipsic hypernatremia by evaluating the osmoregulatory and baroregulatory function tests. Because adipsic hypernatremia is caused by not enough drinking water even for hyperosmolality due to the lack of thirst stimulus, the strategies of treatment are that setting the target body weight when serum osmolality is normal and have the patient drink water until patient reach the target body weight. Adipsic hypernatremia should be considered to be a rare complication of subarachnoid hemorrhage associated with an anterior communicating artery aneurysm.