Background: Toxoplasma gondii is an obligate intracellular parasite in humans and many warm-blooded animals worldwide. Objectives: This study aimed to investigate the diff, erent antiparasitic eff, ects of tellurium oxide (TeO2) nanoparticles against T. gondii. Methods: In this study, we used tachyzoite assay (ocular counting test) to determine the lethal eff, ect of tellurium nanoparticles on parasites. Toxic eff, ects of nanoparticles on macrophages were also evaluated using MTT assay. The type of parasitic cell death (necrosis or apoptosis) was determined by fl, ow cytometric analysis. Results: According to the examination of the parasites by light microscopy, TeO2 nanoparticles had destructive and lethal eff, ects on T. gondii. The results of the MTT assay showed that the toxic eff, ects on macrophages were more signifi, cant at high concentrations (400 , g/mL). Flow cytometric analysis also estimated the percentage of apoptosis (primary and secondary) of the parasites at 56. 97%. Conclusions: According to the fi, ndings, tellurium Oxide nanoparticles have a toxic eff, ect on T. gondii and lead to apoptosis in this parasite. This research boosts diff, erent tests in another parasite.