Nanoparticles have become important scopes of research. The present study made insight into the using of marine bacteria as a new ecofriendly and low cost source for biosynthesis of silver nanoparticles. Fifteen marine bacteria were tested for their capabilities to synthesize silver nanoparticles. Characterization of silver nanoparticles synthesized by the most promising Pseudomonas sp. H64 was performed using UV–Visible spectrophotometer, Fourier transform-infrared spectroscopy, zeta potential, transmission electron microscopy and X-ray. The produced Ag NPs are spherical particles with size of 3-22 nm and negative charge (-14 mV). Different valuable applications of the biosynthesized AgNPs were investigated. The produced AgNPs exhibited promising antibacterial activity against human and fish pathogens (Vibrio parahaemolyticus, Aeromonas hydrophila, Escherichia coli, Streptococcus faecalis, Staphylococcus aureus,  Bacillus subtilis) with inhibition zone diameters (10-37 mm). Moreover, antifungal activity against (Fusarium solani, Rhizoctonia solani; Rhizopus oryzae, Helminthosporium sp.) expressed as inhibition of growth was (77.8±0.68-100%), while no antifungal activity was detected against Aspergillus niger. Antifouling and antioxidant activities were also confirmed. AgNPs exhibited anticancer activity toward (HepG-2, MCF-7, CaCo-2) cell lines. Moreover, AgNPs exhibited bioremediation potential of heavy metals and dyes.