Nanotechnology utilizes green synthesis methods for the production of iron oxide nanoparticles (Fe oxide NPs), favored for their low cost and high efficiency in large-scale industrial applications. In this study, iron oxide NPs were synthesized via a simple biological method using the aqueous extract of Kelussia odoratissima Mozaff leaves. The synthesized nanoparticles were characterized by UV-Vis spectroscopy, which showed an absorption peak at 220 nm, consistent with previous reports of green-synthesized iron oxide NPs. FTIR analysis revealed characteristic peaks at 3430 cm⁻¹ (O-H), 590 cm⁻¹ (Fe-O), 1600 cm⁻¹ (C=C), and 900 cm⁻¹ (C–H out-of-plane bending vibrations), indicating the presence of functional groups responsible for nanoparticle formation and stabilization. SEM imaging showed spherical nanoparticles with an average size ranging from 27 to 33 nm. XRD patterns confirmed the crystalline hexagonal rhombohedral phase of α-Fe₂O₃ with main diffraction peaks at 24.1°, 33.2°, 35.6°, 49.5°, 54.1°, and 62.4°. The antimicrobial activity of the iron oxide NPs was tested against Escherichia coli and Candida albicans, revealing limited inhibition compared to the stronger effects observed with the original plant extract. These findings suggest that bioactive compounds in the Kelussia odoratissima extract play a significant role in antimicrobial activity, and further purification of the nanoparticles may enhance their efficacy.