An intestinal bacterial metabolite of ginseng protopanaxadiol saponin, 20-O-(β-D-glucopyranosyl)-20(S)-protopanaxadiol (compound K), has been reported to induce apoptosis in a variety of cancer cells. However, the precise mechanisms induced by compound K in human hepatocellular carcinoma (HCC) cells remain unclear. In order to examine possible apoptotic mechanisms, we investigated the anticancer effect of compound K in MHCC97-H. MTT assay showed that compound K inhibited the proliferation of MHCC97-H cells with a relatively low toxicity in normal hepatoma cells. Cell cycle progression and cell staining showed an increase in apoptotic sub-G1 fraction. Treatment of MHCC97-H with compound K also induced a reduction in mitochondrial membrane potential (Δψm) and DNA damage. Further study showed that compound K upregulated Fas, FasL, Bax/Bcl-2 ratio and downregulated pro-caspase-9, pro-caspase-3 in a dose-dependent manner, and it also inhibited Akt phosphorylation. These results suggest that compound K significantly inhibits cell proliferation and induces apoptosis in MHCC97-H cells through Fas- and mitochondria-mediated caspase-dependent pathways in human HCC cells.