The purpose of this study was to evaluate the effects of zinc oxide nanoparticles and ions on intestinal tissue histopathology of freshwater crayfish (Astacus leptodactylus) under laboratory conditions. We evaluated two concentrations of zinc oxide nanoparticles and zinc ions (0.5 µm/l and 1.0 mg/l) with a control group. After 14 days of exposure to the nanoparticles of zinc oxide and zinc ions, we obtained intestinal tissue samples from the crayfish. We observed damages such as increased goblet cells and degeneration of the epithelium, edema, increased plasma cells and lymphocytes, and necrosis in the intestines of freshwater crayfish.