microRNAs (miRNAs) have been revealed to participate in some oral cancers and are proved to be effective. In the present study, we tried to explore the biological function of miR-133a in oral squamous cell carcinoma (OSCC) cells. The relationship that C-terminal-binding proteins 2 (CTBP2) was the putative target gene of miR-133a revealed from bioinformatics analysis was further was further validated by dual-luciferase reporter gene assay. In total, 40 patients with OSCC were enrolled for characterization of miR-133a, CTBP2, and Notch signaling pathway-related gene expression in clinical OSCC tissues. Low expression of miR-133a and high expression of CTBP2, Hes1, Notch-1, and Notch-3 were determined in OSCC tissues. OSCC cell lines were transfected with miR-133a inhibitor, miR-133a mimic, or shRNA targeting CTBP2, in response to which cell proliferation, migration, invasion, cell cycle, and apoptosis were evaluated. Transfection of miR-133a mimic induced apoptosis and inhibited OSCC cell proliferation, migration, and invasion and this was demonstrated to be attributable to decreased CTBP2 expression and suppression of the Notch signaling pathway. Taken together, we concluded that miR-133a acted as a tumor suppressor in OSCC through inhibition of the Notch signaling pathway via binding to CTBP2.