Mounting evidence suggests that microRNAs (miRNAs) play important roles in the development of cancer by targeting expression of tumor-related genes. In the present study, downregulation of miR-193b was observed in hepatocellular carcinoma (HCC) tissues and HCC cell lines by quantitative RT-PCR analyses, suggesting that miR-193b is a tumor-suppressor in HCC. More importantly, miR-193b significantly enhanced the cytotoxicity of cisplatin in HepG2 cells by targeting Mcl-1. Knockdown of the Mcl-1 gene by specific siRNA exhibited a function similar to miR-193b on sensitizing HepG2 cells to cisplatin-inducing cytotoxicity. Furthermore, the miR-193b-induced sensitization of HepG2 cells to cisplatin cytotoxicity was abolished by the transfection of Mcl-1 expression plasmid that lacked the 3'-untranslated region (3'-UTR). In addition, activation of caspase-3 was needed for sensitization by miR-193b to cisplatin-mediated cell death. Thus, the present study revealed the downregulation of miR-193b in HCC cells and illustrated a synergistic effect on cisplatin-induced apoptosis by targeting Mcl-1.