BACKGROUND: To synthesize copper nanoparticles utilizing the aqueous extract of Suaeda monoica plant (Salt marsh), a mangrove plant. The nanoparticles synthesized are of small size and high stability, leading to further analysis of the antibacterial activity of gram-positive (S.mutans) and gram-negative Klebsiella species, Salmonella typhi) bacterial strain using the disk diffusion method. AIM: To analyze the antibacterial activity of the biologically synthesized copper nanoparticles against various pathogenic bacteria. MATERIALS & METHOD: Aqueous extract synthesized from Suaeda monoica leaves, CuSO4 utilized as a precursor for copper nanoparticles synthesis. Characterization of NPs, done using UV Vis spectrophotometer. Further, a well diffusion test was done with different concentrations of copper nanoparticles (75μl and 100 μl), with various bacterial strains. The Zones of Inhibition was for the pathogens, with the positive control of Tetracycline and with negative control of methanol.