Changes in intestinal microbiome composition are associated with inflammatory, metabolic, and malignant disorders. We studied how exocrine pancreatic function affects intestinal microbiota. We performed 16S rRNA gene sequencing analysis of stool samples from 1795 volunteers from the population-based study of health in Pomerania who had no history of pancreatic disease. We also measured fecal pancreatic elastase by ELISA and performed quantitative imaging of secretin-stimulated pancreatic fluid secretion. Associations of exocrine pancreatic function with microbial diversity or individual genera were calculated by permutational analysis of variance or linear regression, respectively. Differences in pancreatic elastase levels associated with significantly (P<.0001) greater changes in microbiota diversity than with participant age, body mass index, sex, smoking, alcohol consumption, or dietary factors. Significant changes in the abundance of thirty taxa, such as an increase in Prevotella (q<.0001) and a decrease of Bacteroides (q<.0001), indicated a shift from a type-1 to a type-2 enterotype. Changes in pancreatic fluid secretion alone were also associated with changes in microbial diversity (P=.0002), although to a lesser degree. In an analysis of fecal samples from 1795 volunteers, pancreatic acinar cell, rather than duct cell, function is presently the single most significant host factor to be associated with changes in intestinal microbiota composition.