Many risk factors for pancreatic cancer are related with microbiome alteration. In the past few years, the human microbiome and its relation with the immune system have been linked with carcinogenesis of different organs distant from the gut, including the pancreas. Patterns of oral microbiome associated with periodontitis are associated with an increased risk of pancreatic cancer, possibly because of the increased systemic inflammatory response, or to the capacity of some specific bacteria to alter the host immune response, making it more favorable to cancer cells. Helicobacter pylori infection when affecting the gastric body mucosa with subsequent hypochlorhydria also seems associated with an increased risk of pancreatic cancer. The composition of the intestinal microbiome is different in animal models and in humans with pancreatic cancer who have a distinct microbiome population compared with controls. Some specific bacteria can migrate from the intestine to the pancreas, and their ablation restores the immune system activity through its reprogramming with a switch toward a Th1 response and displays a protective effect toward tumor growth. More research in this area might lead to progress in terms of pancreatic cancer prevention and treatment, possibly in association with immunotherapy.