In the field of nanotechnology, developing an environmentally friendly method for the synthesis of iron nanoparticles (FeNPs) an important aspect. The use of secondary metabolites from plant leaf extract has recently emerged as a novel technology for the synthesis of various nanoparticles, according to recent studies. The leaf extract of Azadirachta indica was used to synthesize iron nanoparticles in this research. The effects of reactant concentrations, reaction temperature and pH of the solution on the synthesis process of iron nanoparticles were studied. The formation of iron nanoparticles in dispersion was monitored using a UV-Visible Spectrophotometer that analyzed absorbance spectra. Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) characterized the morphology of iron nanoparticles and results reveal the particles are spherical in shape with an average size of 48 nm. The following are the ideal conditions for synthesis: leaf extract 15%, [FeCl 3 ] = 1.0 mM, pH 6.0 and temperature 60◦C. The plant biomolecules induce the reduction of Fe 3+ ions to FeNPs and act as a capping and stabilizing agent, which is confirmed by the FTIR technique. Therefore, they have good stability for various applications.