Peri-implantitis, often induced by oral pathogens, is one of the main reasons for the clinical failure of dental implants. The aim of this study was to investigate the biocompatibility, osteogeneic, and antibacterial properties of a cerium oxide (CeO2) coating containing high proportions of Ce4+ valences on a titanium-based dental implant biomaterial, Ti-6Al-4V. MC3T3-E1 cells or bone marrow stem cells (BMSCs) were seeded onto Ti-6Al-4V disks with or without CeO2 coating. Compared to the control, the plasma-sprayed CeO2 coating showed enhanced cell viability based on cell counting kit-8 (CCK-8) and flow cytometry assays. CCK-8, colony-forming unit test (CFU), and live-dead staining illustrated the antibacterial activity of CeO2 coating. Additionally, CeO2 coating upregulated the gene expression levels of osteogenic markers ALP, Bsp and Ocn, with a similar increase in protein expression levels of OCN and Smad 1 in both MC3T3-E1 cells and BMSCs. More importantly, the viability and proliferation of Enterococcus faecalis, Prevotella intermedia, and Porphyromonas gingivalis were significantly decreased on the CeO2-coated Ti-6Al-4V surfaces compared to non-treated Ti-6Al-4V. In conclusion, the plasma-sprayed CeO2 coating on the surface of Ti-6Al-4V exhibited strong biocompatibility, antibacterial, and osteogenic characteristics, with potential for usage in coated dental implant biomaterials for prevention of peri-implantitis.