Synthesis of silver nanoparticles using mangrove aqueous extract of Ceriops tagal and to evaluate the antibacterial efficacy against pathogenic bacteria and fungi. The synthesized silver nanoparticles were characterized by UV-visible spectrophotometer, transmission electron microscopy (TEM) and atomic force microscopy (AFM) techniques. The physical property of nanoparticles in suspension was determined by measuring the zeta potential (ζ-potential) of the colloidal suspension. The standard disk diffusion method was employed to evaluate the antimicrobial activity of silver nanoparticles. The characteristic surface plasmon absorption band of silver nanoparticles (SNPs) was observed around 424 nm. The microscopic images of TEM and AFM showed the presence of spherical shaped nanoparticles with an average size of 30 nm. The zeta potential of the colloidal suspension was found to be -34.18 mV. The SNPs exhibited antimicrobial activity against Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, Bacillus cereus, Proteus mirabilis, Candida albicans, Candida tropicalis and Aspergillus niger. The research provides an important direction in the development of bio-based approach for synthesis of antimicrobial silver nanoparticles.