The authors report a case of Rathke cleft cyst presenting with severe hyponatremia. A 33-year-old man suffered sudden severe headaches, visual changes, dizziness, nausea, vomiting, and a metallic taste in his mouth. Initial laboratory values demonstrated severe hyponatremia. Magnetic resonance imaging revealed a cystic lesion with questionable intracystic hemorrhage, concerning for pituitary apoplexy. Transsphenoidal decompression and drainage of the cyst confirmed the diagnosis of Rathke cleft cyst and resolved the symptoms. Postoperative follow-up studies at 6 months demonstrated normal endocrine function and no evidence of a cyst.