Using clinical specimen analysis, lentivirus transfection, western blotting, RT-qPCR, immunofluorescence, cell adhesion assays, and a GC peritoneal metastasis (GCPM) animal model, we explored galectin-1's role in promoting peritoneal MMT (mesothelial-mesenchymal transition) and enhancing PM through <i>in vivo</i> and <i>in vitro</i> studies. Here, LGALS1 is linked to gastric cancer.