This is the case of a 13-year-old girl. The patient became aware of difficulty using school lunch utensils, chopsticks, and pencils, along with tremors, weakness, and speech difficulties. The patient was referred to our hospital for further examination. Despite detailed tests, no abnormalities were detected. Suspecting psychological factors, the patient was referred to our department in October 20XX. Considering the patient’s developmental history, which indicated autism spectrum disorder as the underlying cause of her symptoms, and her apparent indifference to her symptoms, we made a diagnosis of conversion disorder. The physical symptoms improved with 0.75 mg of aripiprazole, However, about six months after the initial consultation, the patient began experiencing tremors and weakness in her left hand, along with headache, nausea, and stomach pain. Organic causes were ruled out, and the patient was prescribed 2.5 g of yokukansan extract granules, which quickly resolved her symptoms. Yokukansan is a commonly used medication in psychiatry, and is prescribed to treat fits in autism spectrum disorder and the behavioral and psychological symptoms of major neurocognitive disorder. Conversion disorders can be challenging to treat because of the lack of suitable psychotropic medications. However, Kampo medicine can be a useful alternative.