La_0.8Nd_0.1Sr_0.1MnO₃ perovskite was synthesized using the citrate gel method. The crystal structure was studied by X-ray diffraction. The Rietveld refinement reveals a single R-3C rhombohedral structure. The morphological properties were investigated by a scanning electron microscopy, connected to an energy-dispersive X-ray detector for mapping and elements composition, showing a sponge-like structure behavior of agglomerated particles. The band gap energy and the optical properties were studied theoretically by Density-Functional Theory (DFT) calculations. It showed that La_0.8Nd_0.1Sr_0.1MnO₃ exhibited a high photoabsorption property with band gap energy of ≈ 2.5 eV. The methyl orange (MO) degradation properties were studied by measuring time-dependent UV–Visible absorption of the dye solution. The photocatalytic activity was evaluated at different times under visible light and ambient temperature conditions for La_0.8Nd_0.1Sr_0.1MnO₃ solution. A high degradation rate of 80% in 120 min under UV irradiation conditions was observed. It indicated that La_0.8Nd_0.1Sr_0.1MnO₃ presents high photocatalytic efficiency and could be a good candidate for MO degradation.