Objective: To investigate the frequency of parasympathetic neurogenesis and determine its association with tumor budding and prognosis in pancreatic ductal adenocarcinoma(PDAC).Methods: Parasympathetic neurogenesis was defined as the distribution of abnormal parasympathetic nerves in the stroma tissue. Staining of vesicular acetylcholine transporter(VACh T), as a marker for parasympathetic neurogenesis, was performed on a representative specimen of the tumor for 59 PDAC patients with available clinical, pathologic, and follow-up information. Three specimens containing normal pancreatic tissues were stained in parallel. The number of parasympathetic nerve fibers was counted in five high-power microscopic fields(5×0.785 mm~2). Cut-off values were calculated by receiver operating characteristic curve analysis.Results: VACh T-positive parasympathetic nerve fibers were not seen in the stroma of 3 cases of normal pancreatic tissues. In 59 PDAC cases, the range of parasympathetic neurogenesis was 4-38 fibers/(5×0.785) mm~2, with a median of 18 fibers/(5×0.785) mm~2. Patients with parasympathetic neurogenesis >15 fibers/(5×0.785) mm~2 were defined as the high-density group(39 patients, 66.1%), and those with parasympathetic neurogenesis ≤15 fibers/(5×0.785) mm~2 as the low-density group(20 patients, 33.9%). The high-density group had a higher occurrence of tumor budding(P=0.001) and a higher rate of early recurrence(P=0.035). Parasympathetic neurogenesis appeared to be an independent adverse prognostic factor [hazard ratio(HR)=2.45, 95% confidence interval(95% CI): 1.25-4.81, P=0.009], in addition to American Joint Committee on Cancer(AJCC) stage(P=0.010) and tumor budding(P=0.009).Conclusions: Parasympathetic neurogenesis is strongly associated with tumor budding and correlates with an adverse prognosis in PDAC.