Treating latent tuberculosis infection is a strategy for eliminating tuberculosis, and isoniazid is recommended as preventive therapy. However, concerns have been raised regarding the application of isoniazid due to its toxicity, particularly hepatotoxicity; however, biochemical monitoring is not routinely performed during treatment. We herein present a case of fatal isoniazid-induced acute liver failure. The patient's liver function was not periodically examined and isoniazid therapy was continued for 10 days despite the onset of symptoms associated with hepatitis. The patient died four months after hospitalization. It is essential to consider the potential toxicities of isoniazid and establish strategies to prevent acute liver failure.