In this study, toxic effects caused by the degradation of fluoxastrobin, which is a commonly used fungicide where newly synthesized manganese or sulfur-doped TiO2 nanoparticles exist were evaluated. The characterization study of nanoparticles was performed by scanning an electron microscopy (SEM), X-ray diffractometry, Brunau-Emmet-Teller analysis, X-ray fluorescence spectroscopy, and UV-Vis (ultraviolet-visible) reflectance spectra. Subsequently, the photocatalytic performance of nanoparticles, their toxicity, and the photocatalytic degradation products of fluoxastrobin with the same nanoparticles were tested during the two development stages of Xenopus laevis. The LC(50)s of fluoxastrobin were determined on test organisms, and a 5 mg L-1 fluoxastrobin was selected to evaluate the photocatalytic degradation capacity due to toxicity studies. The sublethal effects of the nanoparticles and the degradation product of fluoxastrobin were assessed with embryonic malformations and biochemical marker responses. Sulfur-doped TiO2 was found to be more effective compared to manganese-doped TiO2 for the degradation of fluoxastrobin, photocatalytically. On the other hand, even if the tested nanoparticles were not lethal, they caused effects such as growth retardation and changes in biochemical responses on organisms.