Growing evidence indicates that deregulation of microRNAs (miRNAs) contributes to tumorigenesis. Dysregulation of miR-657 has been observed in several types of cancers, but its biological function is still largely unknown. Our results showed that miR-657 expression can be induced by hepatitis viral proteins and is significantly increased in hepatocellular carcinoma (HCC) tissues. Moreover, introduction of miR-657 dramatically increases proliferation and colony formation of HCC cells in vitro and induces tumor development in immunodeficient mice. Further studies showed that miR-657 directly targets the transducin-like enhancer protein 1 (TLE1) 3′ untranslated region (UTR) and activates nuclear factor kappa B (NF-κB) pathways that contribute to hepatocarcinogenesis. Conclusion: This study identified a mechanism whereby miRNA-657 contributed to HCC through novel cancer pathways and provides new insights into the potential molecular mechanisms of hepatic carcinogenesis. (HEPATOLOGY 2013)