Plasma electrolytic oxidation (PEO) with the ability of tunable surface properties (controlled elemental composition, morphology, porosity, and wettability) showed great promise to act as an antibacterial coating. These mechanically robust coatings with antibacterial and corrosion-resistant properties have diverse applications in medical implants, orthopedic instruments, or surgical tools as well as in oil/gas and marine industries. This chapter provides a comprehensive understanding of the influential factors of PEO coating to tune antibacterial properties, which include electrolyte composition, structural properties, and wettability. This chapter further discusses the applications of antibacterial PEO coatings in the field of biomedical implants, and surgical tools as well as in suitable marine structures. Despite the great success of PEO coatings in orthopedic implants, it demands more attention to realize their full potential in controlling marine biofouling.