Nanotechnology plays a critical role in agriculture and its associated management strategies. The emergence of plant pathogens (phytopathogens) across various crops has posed a threat to global food production, food security, and food safety. The existing control techniques, such as chemical application of pesticides and insecticides, have become outdated due to their drawbacks. Such methods for plant disease control come with the added disadvantage of threat to natural microflora and fauna along with imparting toxicity to the environment. This in turn causes risk to human health. Therefore researchers have been looking for safer alternatives that are equally or more efficient and effective in dealing with phytopathogens along with possessing least amount of toxicity. The generation of nanoparticles (NPs) and its application in plant disease management has intrigued researchers and therefore has revealed an altogether new dimension for the purpose. NP-mediated disease management strategies have proven to be highly proficient and have been explored for a wide range of plant diseases. However, the NPs derived through chemical and physical methods such as electroreduction, use of reagents for reduction/oxidation of metals, may impart toxicity and also cause environmental hazard. Therefore the synthesis of NPs from microbes, known as green synthesis, is far safer in terms of toxicity. The following chapter elucidates the various bacterial and fungal-derived NPs, their characteristic features, and the associated mechanism for protection against plant pathogens.