Zinc oxide nanoparticles (ZnO NPs) and titanium dioxide nanoparticles (TiO2 NPs) are well known as photoreactive nanoparticles (NPs). Various phototoxicities of ZnO NPs and TiO₂ NPs were reported on several organisms. It was still necessary to evaluate the toxicity of photoreactive ZnO NPs and TiO₂ NPs due to species-specific effects under various irradiation conditions. We compared the acute toxicity of Moina macrocopa under visible, ultraviolet (UV) A, and B irradiations, according to the Organization for Economic Cooperation and Development guidelines for the testing of chemicals (Test No. 202). The sensitivity of ZnO NPs for M. macrocopa was UVB>UVA>visible light irradiation. There were no significant lethal and immobile effects of TiO₂ NPs on juveniles under all irradiations and in the tested concentrations of TiO₂ NPs. Photoreactive NPs have a potential and accelerated toxicity on organisms in the ambient environments.