In this study, iron oxide nanoparticles were synthesized using FeCl3 (0.1 M and 0.3 M) with myrtle leaf extract for of methylene blue dye (MBD) degradation under visible light irradiation (100-watt halogen lamp) as environmental application. X-ray diffraction analysis showed the polycrystalline structure of Fe2O3 material with miller indices confirmed the presence of iron oxide with average crystalline sizes (15.59-16.8 nm) synthesized by (0.1M - 0.3mM) concentrations of FeCl3. Field emission-scanning electron microscopy revealed rods-like and spherical shapes of Fe2O3 nanoparticles, with an average particle size of 25 to 67 nm, covered the whole top surface of structure. Moreover, the change of the color of the iron oxide NPs from brown to dark brown enhances the transformation of the properties of the material obtained by adding the biomass which gives the absorbance peaks around 265-350 nm and energy band gaps (3 and 3.7 eV) using UV/VIS spectrometer. The methylene blue degradation efficiencies of Fe2O3 NPs prepared by plant extract and FeCl3 with concentrations (0.1 M and 0.3 mM) were 86.3% after 150 min and 90% after 120 min respectively.