Genetic studies have revealed a critical role of the distal-less homeobox gene 5 () in the pathogenesis of ovarian cancer, lung cancer, and T-cell lymphoma; however, the role and underlying mechanisms of in oral squamous cell carcinoma (OSCC) are largely unknown. In this study, we demonstrated that is up-regulated in OSCC tissues and cell lines, compared with their control groups. The results from our immunohistochemistry (IHC) analyses show that high expression levels of correlated with advanced TNM stages ( = 0.0001), lymph node metastasis ( = 0.0049), poor cellular differentiation ( = 0.0491), location of the tumors ( = 0.0132), and poor prognosis for the patient. We also demonstrated that knockdown of inhibited the viability, proliferation, and colony formation of OSCC cell lines CAL-27 and WSU-HN6 cells, probably by blocking cell cycle in the G1 phase. Furthermore, we revealed that exerts its biological functions via direct regulation of in CAL-27 and WSU-HN6 cells. Ultimately, we have demonstrated that silencing of inhibits the growth of xenograft tumors in vivo, and that affects the progression of OSCC both in vitro and in vivo via directly regulating , providing a potential diagnostic biomarker and therapeutic target for OSCC.