Present study was investigated the antimicrobial activity silver nanoparticles mediated by marine actinobacteria obtained from mangrove creeks of Andaman island. Totally 12 actinobacterial strains were screened for silver nanoparticle synthesis, in which, only one strain NMSA 7 showed a stable synthesis of silver nanoparticles was belongs to the genus Streptomyces sp. The AgNPs was characterized by UV-visible spectrophotometer, XRD analysis, FT-IR and SEM. SEM study of the synthesized AgNPs showed that the nanoparticles were spherical and polydisperse in nature and ranged in size from 3.57 nm to 27.42 nm with an average size of 6.56 nm, respectively. Biosynthesized AgNPs have demonstrated a good antimicrobial activity against the human pathogen Staphylococcus aureus strain. The higher inhibition zone (12 mm) was recorded at a concentration of 500 μl. Silver biosynthesis in accordance with actinobacteria against clinical pathogens will be an efficient approach compared to other chemotherapeutic applications.