Magnetic spinel ferrites that act as heterogeneous catalysts and generate powerful radicals from peroxymono-sulfate (PMS) for the degradation of organic pollutants have received much attention in recent years due to the characteristic of environmental benefits. In this study, NiO-NiFe₂O₄-rGO magnetic nanomaterials were synthesized using a calcinated Ni-Fe-LDH-rGO precursor. The morphology, structure, and chemical constitution were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray energy dispersive spectroscopy (EDS), transmission electron microscope (TEM), N₂ adsorption-desorption isotherms, X-ray photoelectron spectroscopy (XPS), and vibrating sample magnetometer (VSM). The catalytic performance of NiO-NiFe₂O₄-rGO nanoparticles was thoroughly evaluated for peroxymonosulfate (PMS) activation and its removal of rhodamine B (RhB) from water. The influence of different process parameters on the RhB degradation efficiency was examined. Further, the catalytic stability was evaluated. Under optimized conditions, the NiO-NiFe₂O₄-rGO/PMS system was very efficient; RhB fully degraded after 40 min at room temperature. Quenching experiments and electronic paramagnetic resonance (EPR) results suggested that SO₄⁻· and OH· were the main active species in the degradation process. Moreover, NiO-NiFe₂O₄-rGO catalyst was stable without any apparent activity loss after three cycling runs.