Nuts are a rich source of various nutrients that confer numerous health benefits, including dietary fibers, monounsaturated fats, β-carotene, vitamin E, phytochemicals, amino acids, and minerals. This study investigated the impact of cashew nut soluble extract (CNSE) on the intestinal brush border membrane (BBM) morphology, functionality, and gut microbiota via intra-amniotic administration, in vivo (Gallus gallus). The study involved four groups: (1) no injection (control); (2) H2O injection (control); (3) 10mg/ml CNSE; (4) 50 mg/ml CNSE. Results showed that CNSE at 1% and 5% significantly improved duodenal BBM functionality and morphology, including higher Paneth cell numbers and goblet cell diameter in crypt and villi, depth crypt, mixed goblet cell per villi, and villi surface area. CNSE at 1% and 5%, significantly increased the concentration of the beneficial bacteria L. plantarum. Groups with 5% CNSE, overall had better improvements in all the parameters. To further investigate whether CNSE has any beneficial effects on intestinal morphology and other bacteria, long-term studies on Gallus gallus with varying concentrations of CNSE should be conducted. These findings suggest that cashew nut extract may have the potential as a prebiotic agent that can positively modulate the gut microbiota and contribute to overall health. Further research is needed to explore the potential health benefits of CNSE in humans. This paper is currently under review to be published in the MDPI Nutrients Journal, in the section: Phytochemicals and Human Health, under the same research title.