Background and Objectives: Adult-onset Still’s disease (AOSD) is a rheumatic disease characterized by systemic inflammatory symptoms, including intermittent spiking fever, polyarthritis and a distinctive salmon-colored rash. Corticosteroids are the first-line treatment for AOSD. However, corticosteroids are potentially hepatotoxic in certain cases and may complicate the course of the disease. Materials and Methods: A 29-year-old female suffering from fever of unknown origin for two weeks was diagnosed with AOSD according to Yamaguchi’s criteria. She received corticosteroids as the first-line treatment for AOSD and developed acute severe hepatitis. A diagnostic protocol has been performed. Results: Corticosteroid-induced liver injury was confirmed by clinical observation and rechallenge of the drug in this case. The result of liver biopsy also supported the diagnosis. Mycophenolic acid, a disease-modifying antirheumatic drug (DMARD) was chosen as an alternative treatment. AOSD remission was achieved under this treatment after three months. Conclusions: Severe acute hepatitis induced by corticosteroids, although very rare, may be observed in patients with AOSD. Drug-induced liver injury needs to be kept in mind when unexpected acute hepatitis is found. Mycophenolic acid could be a proper substitute medication in these cases.