20(S)-Ginsenoside Rh2 (20(S)-GRh2) exerts important pharmacological effects with regard to the control of human hepatocellular carcinoma (HCC). EZH2 is a potent histone methyltransferase of H3K27me3, which has been determined as an oncogene in many malignancies. The CDKN2A-2B gene cluster encodes three important tumor suppressors, P14, P15 and P16. In this study, the anticancer effect and molecular mechanism of 20(S)-GRh2 on HCC was investigated. Treatment of HCC cells with 20(S)-GRh2 inhibited cell proliferation, migration and induced cell cycle arrest at the G0/G1 phase, and inhibited tumor growth in vivo. We demonstrate for the first time that this effect was specifically mediated by down-regulating expression of EZH2. Further molecular mechanism study indicated that the decreased EZH2 promoted P14, P15 and P16 gene transcription through reducing H3K27me3 modification in the promoter of CDKN2A-2B gene cluster loci. Similarly, silencing of EZH2 by siRNA down-regulated P14, P15, P16 mRNA levels and inhibited HCC cell proliferation. Our results suggested that EZH2 could be a potentially therapeutic target by 20(S)-GRh2 in HCC, which provided a rationale for the development of drugs that inhibited histone methylase as a strategy against various cancers.