A facile green synthesis method was employed to synthesize Bi2O3 nanoparticles using Costus igneus leaf extract as a fuel for combustion synthesis. The calcinated product was characterized using spectroscopic techniques namely X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDXS). The synthesized Bi2O3 nanomaterials were subjected for photocatalytic property using methylene blue as a model organic pollutant present in waste water. The results revealed that Bi2O3 nanoparticles showed 98% degradation efficiency within two hours of visible light irradiation. Furthermore, variation of pH and dye concentration parameters were performed to optimize the photodegradation efficiency of the as synthesized Bi2O3 nanoparticles.