The green synthesis of iron oxide nanoparticles was studied, using Amarnthusblitum variety of spinach as a reducing agent. UV-visible spectroscopy, X-ray diffractometer (XRD), Fourier transform infrared spectroscopy, and scanning electron microscopy (SEM) were used to examine the structural and morphological properties of the produced Fe3O4 nanoparticles. SEM investigation revealed that the synthesized nanoparticles are spherical, highly crystalline, and agglomerated, with sizes ranging from 30 to 65 nm. Nanoparticles were used as an adsorbent to remove copper from wastewater. The adsorption of copper onto iron oxide nanoparticles from aqueous solution was investigated by varying contact time, adsorbent dosage, and agitation speed. Copper removal was 98% with 350 rpm agitation, 60-minute contact period, 0.05g adsorbent dosage, pH of 6±0.2at room temperature. The equilibrium adsorption data were evaluated using Freundlich and Langmuir isotherms, and the Freundlich model best describes copper adsorption. The kinetic analysis revealed that the adsorption of copper follows pseudo-second-order models with rate constants of 0.9838. The current study demonstrates that Fe3O4 nanoparticles can be used as effective green adsorbents for the removal of copper from wastewater.