AbstractEpithelial‐to‐mesenchymal transition (EMT) is key to invasion and metastasis by oral squamous carcinoma (OSCC) cells. MicroRNAs (miRNAs) such as miRNA‐146a are known to be upregulated in OSCC. However, it is unclear whether they are involved in driving EMT. Here, we investigated the effect of miR‐146a overexpression on proliferation, migration, and EMT in OSCC cells. OSCC cells were transfected with a plasmid expressing miR‐146a precursor. Cell lines that stably overexpressed miRNA‐146a were assessed for proliferation, colony formation, and invasiveness in vitro. Expression of markers and regulators of EMT, cell motility, and invasion were measured by qRT‐PCR and western blot. Potential miRNA‐146a binding sites in the 3′UTR of ST8SIA4 were identified by bioinformatic analysis. To confirm that miRNA‐146a binds to and regulates ST8SIA4, we transfected OSCC cell lines with miRNA‐146a mimics and a luciferase reporter construct containing either the wild type or mutant 3′UTR of ST8SIA4. OSCC cell lines that overexpressed miR‐146a displayed higher proliferation, colony formation, invasion, and MMP‐2 activity than cells transfected with a control vector. Overexpression of miR‐146a also decreased expression of the epithelial cell marker E‐cadherin and increased expression of Twist1, a transcription factor that promotes EMT, as well as markers associated with mesenchymal cells (vimentin and N‐cadherin) and tumor invasion (p‐paxillin and p‐cortactin). Luciferase expression was lower in OSCC cells transfected with miRNA‐146a mimics or with luciferase constructs carrying the wild type, but not mutant, 3′UTR of ST8SIA4. Overexpression of miR‐146a promotes EMT phenotypes and may drive tumorigenesis and progression in OSCC, making it a useful target for future OSCC treatments.