A second-generation direct-acting antiviral agent, simeprevir, now provides a new treatment option for hepatitis C virus (HCV) infection with good safety profile in combination with pegylated interferon and ribavirin. We herein report a rare case of severe liver injury under simeprevir plus pegylated interferon/ribavirin therapy. We initiated this therapy in a 65-year-old male with treatment-naïve genotype 1b HCV. On day 28, the patient's HCV-RNA was successfully eliminated, and his liver function was fully restored. However, on day 49, the serum alanine aminotransferase level was elevated at 700 IU/L. The HCV-RNA titer was still undetectable and the involvement of other possible viruses was negligible. A liver biopsy performed on day 60 showed an acute hepatitis pattern. The discontinuation of therapy alone successfully improved his liver damage on day 84. No other treatments such as steroids were required. According to the diagnostic criteria for drug-induced liver injury in Japan (DDW-J2004), the liver injury observed in this case can be associated with the administration of simeprevir plus pegylated interferon/ribavirin therapy. In conclusion, simeprevir plus pegylated interferon/ribavirin should be used with caution, as these agents may cause unreported serious adverse events including severe liver injury, despite their clinical safety profile.