Adenanthin, a natural diterpenoid isolated from the leaves of Isodon adenanthus, has recently been reported to induce leukemic cell differentiation by targeting peroxiredoxins (Prx) I and II. On the other hand, increasing lines of evidence propose that these Prx proteins would become potential targets to screen drugs for the prevention and treatment of solid tumors. Therefore, it is of significance to explore the potential activities of adenanthin on solid tumor cells. Here, we demonstrate that Prx I protein is essential for the survival of hepatocellular carcinoma (HCC) cells, and adenanthin can kill these malignant liver cells in vitro and xenografts. We also show that the cell death-inducing activity of adenanthin on HCC cells is mediated by the increased reactive oxygen species (ROS) levels. Furthermore, the silencing of Prx I or Prx II significantly enhances the cytotoxic activity of adenanthin on HCC, whereas the ectopic expression of Prx I and Prx II but not their mutants of adenanthin-bound cysteines can rescue adenanthin-induced cytotoxicity in Prxs-silenced HCC cells. Taken together, our results propose that adenanthin targets Prx I/II to kill HCC cells and its therapeutic significance warrants to be further explored in HCC patients.