Bacterial plant diseases are the main cause of high agricultural losses worldwide, requiring the development of effective, sustainable, and environmentally friendly management strategies. Chitosan is a natural chitin-derived biopolymer that has shown promise as an active ingredient due to its biocompatibility, biodegradability, and innate antimicrobial properties. Recent advances in nanotechnology have enabled the production of chitosan nanoparticles (CNPs) that are more effective against bacteria than bulk chitosan due to their larger surface area, improved solubility, and greater affinity for microbial cells. This chapter discusses the synthesis methods, physicochemical properties, and antibacterial activity of CNPs against bacterial phytopathogens. CNPs destabilize bacterial membranes, disrupt biofilm formation, and induce systemic resistance in plants, providing a versatile solution for disease control. Multiple studies have demonstrated the efficacy of CNPs against critical bacterial diseases such as bacterial blight of rice, fire blight of apples and pears, and bacterial wilt of tomatoes. Additionally, chitosan nanoparticles act synergistically with traditional bactericides, reducing the use and of chemicals ecological impact. Their potential is further confirmed by field trials and greenhouse experiments in real agricultural environments. Despite these promising results, challenges remain related to large-scale production, standardization, regulatory approval, and understanding the long-term environmental impact. Overall, CNPs are an innovative and sustainable resource that can be integrated into plant disease management strategies, and fit into global efforts to make agriculture greener and safer agriculture. Future research should focus on improving formulations, understanding the interactions between plants, microbes, and nanoparticles, and developing cost-effective delivery systems for practical applications.