This study presents an eco-friendly approach for synthesizing iron oxide nanoparticles using an extract from Argemone mexicana leaves, which function as reducing and stabilizing agents. The nanoparticles were thoroughly characterized using a range of techniques, including ultraviolet-visible (UV-vis) spectrophotometry, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray diffraction (XRD), and zeta potential analysis. The synthesized Fe-NPs demonstrated notable antioxidant activity, as confirmed by assays involving 2,2′-azino-bis-(3-ethylbenzothiazoline-6-sulfonic) acid (ABTS) and 2,2-diphenyl-1-picrylhydrazyl (DPPH). The results highlight the significant antioxidant potential of these Fe-NPs. This research introduces a sustainable and innovative synthesis method for Fe-NPs, emphasizing their promising applications, particularly in fields related to antioxidant properties, as evidenced by the conducted antioxidant assays.