We report the case of an 89-year-old man with fever and consciousness change who was found to be in thyroid storm. The patient was apathetic before this admission. The patient's general condition and mental status improved after prompt treatment for his thyrotoxicosis and he was discharged 4 weeks later with good mental and physical activity. Apathetic hyperthyroidism is a less common occult presentation of thyrotoxicosis when apathy, inactivity and depression replace the readily recognizable manifestations of hyperthyroidism. Although it can occur at any age, it is more commonly encountered in elderly patients. The apathetic presentation may enhance the difficulty in diagnosing thyroid crisis. A high index of clinical suspicion is needed in general practice.