MicroRNA (miR)-200c suppresses the initiation and progression of oral squamous cell carcinoma (OSCC), the most prevalent head and neck cancer with high recurrence, metastasis, and mortality rates. However, miR-200c -based gene therapy to inhibit OSCC growth and metastasis has yet to be reported. To develop an miR-based gene therapy to improve the outcomes of OSCC treatment, this study investigates the feasibility of plasmid DNA encoding miR-200c delivered via non-viral CaCO 3 -based nanoparticles to inhibit OSCC tumor growth. CaCO 3 -based nanoparticles with various ratios of CaCO 3 and protamine sulfate (PS) were utilized to transfect pDNA encoding miR-200c into OSCC cells and the efficiency of these nanoparticles was evaluated. The proliferation, migration, and associated oncogene production, as well as in vivo tumor growth for OSCC cells overexpressing miR-200c were also quantified. It was observed that, while CaCO 3 -based nanoparticles improve transfection efficiencies of pDNA miR-200c , the ratio of CaCO 3 to PS significantly influences the transfection efficiency. Overexpression of miR-200c significantly reduced proliferation, migration, and oncogene expression of OSCC cells, as well as the tumor size of cell line-derived xenografts (CDX) in mice. In addition, a local administration of pDNA miR-200c using CaCO 3 delivery significantly enhanced miR-200c transfection and suppressed tumor growth of CDX in mice. These results strongly indicate that the nanocomplexes of CaCO 3 /pDNA miR-200c may potentially be used to reduce oral cancer recurrence and metastasis and improve clinical outcomes in OSCC treatment. (227 words).