Diseases associated with metabolic syndromes are of major concern in developed countries. Nonalcoholic steatohepatitis (NASH) is one of the manifestations of metabolic syndrome in the liver. Previous studies have shown that NASH is also caused by malnutrition. In the present study, a case of malnutrition-associated NASH in a 66-year-old female with anorexia nervosa is reported. The patient had a body mass index (BMI) of only 11.1 kg/m2 and serum alanine aminotransferase levels of 1,495 IU/l. Steatohepatitis with fibrosis was confirmed by percutaneous liver needle biopsy. Total parenteral nutrition was conducted at first, followed by the administration of Stronger Neo-Minophagen C (a glycyrrhizin-containing preparation), ursodeoxycholic acid and prednisolone. The abnormal elevation of aminotransferase levels of the patient was prolonged and total bilirubin levels increased. Pioglitazone (15 mg/day), which has been identified to be effective for nonalcoholic steatohepatitis, was then administered. This resulted in marked reductions in aminotransferase and bilirubin levels within three months. Histological improvement of the liver was also confirmed by percutaneous liver needle biopsy after one year. The observations in the present case suggest that pioglitazone may be useful for the treatment of malnutrition-associated NASH.