<p>Pancreatic cancer remains one of the deadliest malignancies, primarily due to its highly immunosuppressive tumor microenvironment (TME) and poor response to conventional therapies. Increasing evidence highlights the gut microbiota as a pivotal regulator of antitumor immunity, modulating T cell activation, macrophage polarization, and dendritic cell function. Microbial communities and their metabolites can either inhibit or enhance immune surveillance, thereby influencing the efficacy of immunotherapies such as immune checkpoint inhibitors (ICIs) and CAR-T cell therapy. Approaches including dietary modulation, probiotics, fecal microbiota transplantation (FMT), and microbial metabolite supplementation show promise in restoring immune homeostasis and improving treatment outcomes. Additionally, gut microbiome profiling has emerged as a potential source of biomarkers for predicting therapeutic response and immune-related adverse events. This review summarizes current insights into microbiota–immune interactions in pancreatic cancer, emphasizes microbiome-targeted therapeutic strategies, and explores future opportunities for precision immunotherapy guided by microbial modulation.</p>