A ternary Cu2O-BiVO4-WO3 nanocomposite (NC) was prepared and characterized by XRD, DRS, SEM-EDX, TEM, FTIR, and photoluminescence (PL) spectroscopy. The composite was then used in the photocatalytic degradation of sulfasalazine (SSZ) aqueous solution. The pH(pzc) of 6.9 was estimated for the composite. The average size of 8.6 nm was also estimated for the composite crystals by the Williamson-Hall method. The band gap energies of 2.4, 2.46, 3.0, and 2.62 eV were obtained for Cu2O, BiVO4, WO3, and the composite, respectively. The composite showed the lowest PL intensity and the highest photocatalytic activity due to the lowest electron/hole recombination process. Interaction effects between the variables on SSZ photodegradation were studied by designing the experiments by applying the response surface methodology (RSM) approach. The optimized run included by pH: 3.5, catalyst dosage: 0.3 g/L, irradiation time: 40 min, and C-SSZ: 8 g/L. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.