In this book, we would like to focus on the antibacterial activity of metal oxide nanoparticles (NPs) like zinc oxide, magnesium oxide, iron oxide and copper oxide etc. Most of the metal oxides were found to be as good antibacterial agents against the various gram positive and gram negative bacteria and was dependent on size and concentration. Antibacterial activity of metal oxide nanoparticles has received significant interest in the world in view of recent developments in the nanotechnology. Metal oxide NPs exhibit attractive antibacterial properties due to increased specific surface area as the reduced particle size leading to enhanced particle surface reactivity. For example, one functional application of the metal oxide like ZnO is the antibacterial bioactivity in food packaging industry where ZnO-NPs are used as an antibacterial agent toward foodborne diseases. Proper incorporation of ZnO-NPs into packaging materials can cause interaction with foodborne pathogens, thereby releasing NPs onto food surface where they come in contact with bad bacteria and cause the bacterial death and/or inhibition.