As like natural enemies of nematodes, nematophagous bacteria can be used for efficient management of plant parasitic nematodes. Nematophagous bacteria either inhibit or kill the nematodes by parasitizing, production of secondary metabolites (toxins, antibiotics, enzymes), compete for nutrients, induced systemic resistance (ISR) thereby promotes plant health. In this chapter, details of different nematophagous bacteria i.e., obligate parasitic bacteria, cry protein forming bacteria, opportunistic parasitic bacteria, rhizobacteria and endophytic bacteria and its mode of action is discussed at molecular level. Understanding pathogenesis at molecular level helps in effective utilization of nematophagous bacteria as biocontrol agents against nematodes without any adverse effects on human health and environment as seen in case of nematicides.