In this work, we have prepared iron oxide nanoparticles (Fe2O3 NPs) by a simple protocol using aqueous extract of Raphanus sativus leaves. The prepared Fe2O3 NPs were characterized by UV–Vis spectrophotometer, FTIR, powder XRD, FESEM, EDS and DRS studies. The size of the prepared nanoparticles was found to be 48.19 nm with rhombohedral structure. The catalytic efficiency of the prepared Fe2O3 NPs was monitored by the degradation of harmful dyes like methylene blue (MB) and methyl red (MR) using hydrogen peroxide (H2O2) as an oxidizing agent. The results supported that the degradation follows pseudo-first-order kinetics and the prepared Fe2O3 NPs can be an excellent catalyst for the water treatment process. © 2020, Springer Science+Business Media, LLC, part of Springer Nature.