Iron oxide nanoparticles (IONPs) have attracted considerable interest for diverse fundamental and biomedical applications IONPs play significant roles in nanotechnology and considered to be one of the prominently used particles due to their lesser toxicity and high chemical stability. The undertaken study describes biological synthesis of Iron Oxide nanoparticles (Fe2O3 NPs) using leaf Castor extract along with evaluation of the antibacterial efficiency. To synthesis the Iron oxide nanoparticles, freshly extract was added to 0.1 M solution of Iron chloride hexahydrate in a 5:1 volume ratio. The synthesis of Fe2O3 NPs was confirmed via several characterizations. UV–Vis analysis detected a characteristic absorbance at the spectral range of 380 nm and the energy gap was (2.4 ev). The functional groups which are responsible for nanoparticle formation have been identified by Fourier transformed infrared spectroscopy (FTIR). NPs' XRD pattern doesn't have a definite crystalline peak, thus it is obvious that IONPs are amorphous compounds by nature. α-Fe2O3 NPs are more efficient to inhibit the growth of Staphylococcus aureus as the zone of inhibition (ZOI) ranging from 17-22 mm and the maximum ZOI was 22 mm at concentration 75 µg/ml have been observed. It has been seen in this study that by increasing the concentration of the α-Fe2O3 nanoparticles, the growth inhibition has also been increased. Keywords: Green Synthesis, Iron Oxide Nanoparticles, leaf Castor, Inhibition Zone.