Allophylus serratus mediated silver nanoparticles biosynthesis, characterization, and antimicrobial activity were described. The synthesis of silver nanoparticles was confirmed by visual observation: UV-Vis spectrum, X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), and Fourier Transform Infra-Red (FTIR). UV-Vis spectroscopy studies showed that the absorption spectra of synthesized silver nanoparticles from leaf and callus extracts had absorbance peak range of 440 nm and 445 nm, respectively. The X-RD pattern revealed the presence of crystalline, dominantly spherical silver nanoparticles in the sample having size ranging from 42 to 50 nm. The XRD peaks 38.2°, 44.1°, 64.1°, and 77.0° for leaf extract and 38.1°, 44.3°, 64.5°, 77.5°, and 81.33° for callus extract can be assigned the plane of silver crystals (111), (200), (220), and (311), respectively, and indicate that the silver nanoparticles are face-centered, cubic, and crystalline in nature. SEM and EDS analysis also confirmed the presence of silver nanoparticles. The FTIR results showed the presence of some biomolecules in extracts that act as reducing and capping agent for silver nanoparticles biosynthesis. The synthesized silver nanoparticles showed significant antibacterial activity against Klebsiella pneumoniae and Pseudomonas aeruginosa.