Waterborne bacterial disorders pose a serious threat to global health, particularly in regions with limited access to safe drinking water. The increase in antibiotic resistance has intensified the need for innovative antimicrobial strategies. Among these, green-synthesized nanoparticles, particularly those prepared from plant sources, provide a sustainable and effective solution. This chapter focuses on the green synthesis of nanoparticles using plants, emphasizing their biocompatibility, environmental-friendliness, and low-cost production. Detailed antibacterial mechanisms, like reactive oxygen species generation, cell membrane disruption, and ion leaching, are addressed, including their varying efficacy against Gram-positive and Gram-negative bacteria. Specific focus is given to the application of silver, zinc oxide, copper, and gold nanoparticles against key waterborne pathogens including Escherichia coli, Vibrio cholerae, and Salmonella typhi. The chapter also assesses the incorporation of these nanoparticles into water treatment systems, while addressing critical concerns like nanotoxicity, environmental persistence, and biosafety. By integrating nanotechnology and natural plant compounds, this emerging field holds potential for sustainable solutions against waterborne bacterial problems.