The effect of antioxidant (Antox) on Giardia lamblia and Microsporidium sp. in rats and mice respectively was studied. Parasitologic effect was assessed by the mean parasitic count in infected animals' stool treated and non-treated, and infection intensity in stained section. Biochemical by measuring activities of lactate dehydrogenase (LDH), superoxide dismutase (SOD), malondialdehyde (MDA), myeloperoxidase (MPO) levels and cytokine induced neutrophil chemoattractant-1 (CINC-1) in intestinal homogenates in these animals as shown by cell injury, lipid peroxidation and neutrophil infiltrations. The present results showed that Antox significantly exacerbated G. lamblia and Microsporidium sp. This was manifested by a significant increase in number of G. lamblia cysts and trophozoites in stool and intestinal sections of treated infected rats. Also, microsporidian spores were significantly higher in stool of treated infected mice and infection intensity increased in the intestinal sections. The biochemical study showed a significantly higher degree of cell injury, lipid peroxidation and intestinal neutrophils accumulation in non-treated infected animals whether with G. lamblia or microsporidia. The changes reduced after treatment in giardiasis but none in microsporidiosis. The results were tabulated photographed, and critically discussed.