Abstract: Bile acids play a crucial role in maintaining lipid metabolism and intestinal homeostasis in weaned piglets, yet their systematic mechanisms in alleviating weaning stress remain to be fully elucidated. This review systematically analyzed the effects of weaning stress on intestinal barrier function, microbiota and immune responses in piglets. It highlights the role of bile acids as signaling molecules in activating receptors such as the farnesoid X receptor and G protein-coupled bile acid receptor 5, thereby regulating signaling pathways including myosin light chain kinase and phosphatidylinositol 3-kinase/protein kinase B. These mechanisms increase expression of tight junction proteins, improve villus morphology, modulate immune function, and stabilize gut microbiota. The review also summarized the beneficial effects of dietary bile acid supplementation on increasing average daily gain, reducing diarrhea rate, and promoting intestinal development in weaned piglets. Finally, future research directions were proposed to further explore bile acids as a nutritional intervention strategy, provide a theoretical basis for mitigating weaning stress and ensuring intestinal health in piglets.