Aberrant microRNA (miRNA or miR) expression has been reported to contribute to the pathogenesis of hepatocellular carcinoma (HCC). However, the involvement of specific miRNAs in HCC remains to be elucidated. The present study aimed to investigate the potential role of miR-200b and the mechanism underlying its function in hepatocarcinogenesis. The results of the present study demonstrated that the expression levels of miR-200b were significantly reduced in HCC tissue samples, as compared with normal liver (NL) and para-tumorous (PT) tissue samples. The results also revealed that miR-200b expression levels in HepG2 cells were significantly decreased compared with those in L02 cells. In addition, western blotting and reverse transcription-quantitative polymerase chain reaction demonstrated that the expression levels of DNA methyltransferase 3a (DNMT3a), a possible target gene for miR-200b, were significantly higher in HCC tissue samples, as compared with those in NL and PT tissue samples. Furthermore, the data suggested that DNMT3a was a direct target gene of miR-200b. Upregulated miR-200b expression in HepG2 cells led to a decrease in DNMT3a expression levels, and an inhibition of cell proliferation. These results suggested that miR-200b has an important role in hepatocarcinogenesis and acts by downregulating DNMT3a expression. Thus, miR-200b may be a promising target for HCC treatment.