This study presented a green method for synthesizing silver nanoparticles (AgNPs) from an aqueous solution of silver nitrate using Sapindus mukorossi fruit pericarp extract as a reducing and capping agent. The prepared AgNPs were characterized using UV–Visible spectroscopy (UV–Vis), high-resolution transmission electron microscope (HR-TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and thermal gravimetric analysis (TGA). The UV–Vis spectra demonstrated surface plasmon resonance for synthesized AgNPs around 428–430 nm. The XRD and HR-TEM analyses showed the crystalline and spherical nature of AgNPs with an average size of 17.3 nm together with unimodal size-distribution. The FTIR measurements were performed to identify the possible functional groups responsible for the efficient reduction of silver ions, and stabilization of the AgNPs. The TGA thermogram confirmed the presence of organic compounds capping the bio-synthesized AgNPs and stabilizing them. The green synthesized AgNPs also exhibited effective antibacterial activities against both gram-positive (Staphylococcus aureus) and gram-negative (Pseudomonas aeruginosa) microorganisms.