Conventional chemotherapy of liver cancer fails to provide satisfactory remission and may cause serious side effects, thus it is crucial to derive alternative treatments that effectively inhibit cancer cell growth with known mechanisms of action. In the present study, we investigated the anti-carcinogenic effects of Coptis chinensis and its major constituent, berberine, in HepG2 hepatocellular carcinoma (HCC) cells and attempted to elucidate the underlying mechanism, including involvement of the nonsteroidal anti-inflammatory drug (NSAID)-activated gene (NAG-1). Inhibition of cell proliferation, induction of apoptosis and cell cycle arrest at the G2/M phase were observed in HepG2 cells treated with Coptis chinensis or berberine. The pro-apoptotic effects were associated with corresponding down-regulation of Bcl-2, activation of procaspase-3 and -9 as well as cleavage of poly (ADP-ribose) polymerase. We further demonstrated the involvement of NAG-1 in the pro-apoptotic events following prior activation of its upstream transcriptional factor early growth response gene (Egr-1). This was confirmed by increased NAG-1 promoter activity preceded by the elevation of Egr-1/ DNA binding activity. Our results suggest that both Coptis chinensis and berberine are potential anti-carcinogenic agents in treating HCC by inducing cell cycle arrest and promotion of apoptosis, while NAG-1 is a molecular target during the drug-induced pro-apoptotic action in HepG2 cells.