In the present investigation a fast, convenient and environment friendly method has been used for the synthesis of silver nanoparticles (AgNPs) by biologically reducing 30 ml of 4 mM AgNO3 solution with extract of 2 ml of 5 % (m/v) mango leaf under optimum conditions (pH of 11). The formation of silver nanoparticles was indicated by the colour changes from colourless to light yellow then to yellow brown and finally reddish brown. Biosynthesized AgNPs were also characterized by UV-Visible and FT-IR spectroscopy. The reduction process was simple and convenient to handle and was monitored by UV-Visible spectroscopy that showed surface plasmon resonance (SPR) of the AgNPs at 418 nm. The presence of active flavanoids, phenolic groups, alkaloids, and carbohydrates which were in the biomass of the mango leaf extract before and after reduction was identified using qualitative screening methods (observing the colour changes) and FT-IR Spectroscopy. The FT-IR also showed that there were (3430, 2333, 2102, 1638 and 647) cm-1 newly formed peaks that is different from the spectrum of the pure mango leaves of (3484, 1627 and 703) cm-1. These biologically synthesized AgNPs were tested for their antimicrobial activity against four human pathogens i.e. S. typhi, E. coil, S. aureus and S. pyrogens. They were found to have significant effect in controlling the growth of the human pathogens with a maximum zone of 22 mm in S. typhi and a minimum zone of 7 mm in S. pyrogens. Keywords: AgNPs, Mango leaf, Green synthesis, UV-Vis, FT-IR, Antimicrobial activity