The Bmi1 gene has been reported to play important roles in cancer initiation and progression. The aim of this study was to investigate the effects of RNA interference (RNAi)-mediated silencing of Bmi1 gene expression on the proliferation and invasiveness of hepatocellular carcinoma (HCC) cells and on the efficacy of chemotherapy in HCC patients. The Bmi1 gene was silenced by Bmi1-siRNA (small interfering RNA) in the human HCC cell lines HepG2 and Bel-7402, and the gene expression levels were assayed by real-time quantitative reverse transcription-polymerase chain reaction (qRT-PCR) and western blotting. The proliferation and migration of Bmi1-silenced tumor cells and their sensitivity to 5-FU treatment were determined by Cell Counting Kit-8 (CCK-8), transwell assays and 4',6-diamidino-2-phenylindole (DAPI) staining and flow cytometry, respectively. Bmi1-siRNA inhibited the Bmi1 expression at both the mRNA and protein levels in HCC cells. Proliferation and migration of HCC cells treated with Bmi1-siRNA was significantly lower compared to that of the control cells. Moreover, Bmi1 gene silencing increased the percentage of apoptotic cells treated by 5-FU and decreased the IC50 values of 5-FU to a greater extent. Downregulation of the Bmi1 gene by RNAi can inhibit the proliferation and invasivesness of HCC cells and increase their sensitivity to 5-FU treatment.