Titanium orthopaedic implants present a risk of infection and require the development of antibacterial, but still biocompatible and non-resistant coatings. Magnesium oxide (MgO) coatings were prepared on micro-arc oxidized titanium by electrophoretic deposition for 15, 30, 45, or 60 s. Nano-sized MgO particles agglomerated to form homogeneous coatings with surface coverage increasing with the duration of deposition. The four groups produced antibacterial rates of 1%, 69%, 83%, and 84% after co-cultured with S. aureus for 6 h, and 81%, 86%, 89%, and 98% after co-cultured for 24 h. Electron and fluorescence microscopies showed decreasing density of bacterial cells and proportion of living cells with increasing time of deposition. Mouse osteoblasts seeded on the four groups had survival rates of 108%, 89%, 53%, and 27% on day 1, and 139%, 117%, 112%, and 66% on day 5. Proportion of dead cells on the coated samples increased with increasing time of deposition but less than 5% on day 5. These results indicate that MgO coatings prepared by electrophoretic deposition for 30 s is reasonable in vitro antibacterial activities and cytocompatibility.