Hepatocellular carcinoma (HCC), one of the most common maligant cancers in the world, is difficult to diagnose in the early time. MicroRNAs (miRNAs), small non-coding RNAs, perform vital functions in cellular differentiation, metabolism and physiological processes. MiR-133a acts as a tumor suppressor in breast, lung and gastric cancer, while the molecular circadian mechanism has not been clear in HCC. In the present study, we certified that the expression of miR-133a decreased in HCC tissues and cell lines and that miR-133a inhibited proliferation, migration and invasion of hepatocellular carcinoma cells. Fos-related antigen 2 (FOSL2), also named FRA-2, was predicted to be a downstream target of miR-133a based on bioinformatic analysis and the prediction was verified by Western Blot, qRT-PCR and luciferase reporter assay. In addition, there was a negative correlation between miR-133a and FOSL2 expression in HCC samples. Furthermore, we verified that overexpression of miR-133a suppressed biological behaviour of HCC through TGF-β/Smad3 signaling pathway. In brief, miR-133a may be a potential prognostic biomarker and may thus be a new therapy in HCC.