Hypothalamic-pituitary-adrenal axis impairment in anorexia nervosa is marked by hypercortisolemia, and psychiatric disorders occur in the majority of patients with Cushing's syndrome. Here we report a patient diagnosed with anorexia nervosa who also developed Cushing's syndrome. A 26-year-old female had been treated for anorexia nervosa since she was 17 years old, and also developed depression and paranoid schizophrenia. She was admitted to the Department of Endocrinology, Metabolism, and Internal Medicine with a preliminary diagnosis of Cushing's syndrome. Computed tomography revealed a 27 mm left adrenal tumor, and she underwent laparoscopic adrenalectomy. She was admitted to hospital 6 months after this procedure, at which time she did not report any eating or mood disorder. This is a rare case report of a patient with anorexia nervosa in whom Cushing's syndrome was subsequently diagnosed. Diagnostic difficulties were caused by the signs and symptoms presenting in the course of both disorders, ie, hypercortisolemia, osteoporosis, secondary amenorrhea, striae, hypokalemia, muscle weakness, and depression.