Nano-particles possess unique, electrical, optical as well as biological properties and are thus applied in catalysis, cosmetics, and anti-bacterial activity by using leaves extract of Azadirachta indica (neem). Under different experimental conditions green-Iron based nanoparticles (FeNPs) were synthesized. Green-synthesized FeNPs were observed qualitatively by color differentiation pattern (color changed from brown to black) and the formation and stability of the reduced FeNPs in the colloidal solution were monitored by UV-Vis spectrophotometer (range of 200-700 nm). Fourier Transform Infrared (FTIR) spectrum (range of 4,000-400 cm-1) established the presence of phenolic compounds in the leaves extract of Azadirachta indica. Therefore, bioactive compounds such as saponins, flavonoids, steroids, and glycosides were detected to be present in the leaves of Azadirachta indica. Anti-bacterial activity shown by FeNPs against pathogen such as E. coli and S. aureus, by agar-disc diffusion method. The zone of inhibition (ZOI) by FeNPs on S. aureus was 14.8 mm while on E. coli was 9.2 mm. Thus, the synthesized FeNPs proved to have very high anti-bacterial activity on both S. aureus and E. coli. These results show that the green-synthesis of FeNPs using leaves extract of Azadirachta indica successfully proved the anti-bacterial potential and phytochemical properties.