<p>A novel hierarchical hybrid nanostructure of reduced graphene oxide-supported NiMn₂O₄ (NiMn₂O₄@rGO) was successfully synthesized via a simple hydrothermal method. X-ray diffraction (XRD), Raman, Field emission scanning electron microscopy (FESEM), Transmission electron microscopy (TEM), N₂ adsorption-desorption and X-ray photoelectron spectroscopy (XPS) analyses confirmed the formation of vertically aligned ultrathin NiMn₂O₄ nanosheets on rGO sheets with a mesoporous structure. The composite exhibited a high specific surface area of 101.7 m²/g and a reduced band gap of 2.90&#xa0;eV, compared to 39.2 m²/g and 3.08&#xa0;eV for pristine NiMn₂O₄. The photocatalytic activity was evaluated under UV irradiation for the degradation of organic pollutants including Orange Green (OG), Eosin Yellow (EY) and Hydroquinone (HQ). The NiMn₂O₄@rGO nanocomposite achieved degradation efficiencies of 95.69%, 99.60%, and 91.88% for OG, EY, and HQ, respectively, within 60–90&#xa0;min. Kinetic studies followed pseudo-first-order kinetics, with rate constants of 71.47 × 10⁻³ min⁻¹ (OG), 208.72 × 10⁻³ min⁻¹ (EY), and 40.36 × 10⁻³ min⁻¹ (HQ). The catalyst retained over 90% of its activity after three reuse cycles. These results suggest that NiMn₂O₄@rGO is a promising photocatalyst for efficient degradation of hazardous organic contaminants in wastewater.</p>