The need to find effective and environmentally friendly ways to prevent pharmaceuticals from contaminating water is due to the growing concern about water pollution caused by hazardous organic pollutants. Photocatalysis is crucial for the degradation of organic pollutants. For this reason, many uses of nanostructured perovskite in various energy and environmental fields have aroused interest. The innovative aspect of this study is the use of SrNiO3 synthesis via the one-pot citrate nitrate method in photocatalysis. The sample was calcined at 450 °C and 900 °C for 5 h. Crystalline phase purity, morphology, surface area, pore size, and optical properties were investigated through X-ray diffraction (XRD), scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET), Barrett-Joyner-Halenda (BJH), Fourier transform infrared spectroscopy (FTIR), and diffuse reflectance spectroscopy (DRS). The prepared sample of SrNiO3 was used as a photocatalyst for the photodegradation of naproxen, one of the most common pharmaceutical compounds detected in wastewater. The effects of catalyst dose, naproxen amount, and reaction kinetics were investigated. After 60 min of UV irradiation exposure, the photocatalytic removal efficiency was found to be optimal using 1 g/L of SrNiO3. In summary, perovskite SrNiO3 exhibited excellent physicochemical and mechanical stability after five cycles of reaction.