Backgrounds/AimsDiabetes mellitus (DM) is a known risk factor for morbidity, length of hospital stay, or mortality after surgery, however, its impact on postoperative course and long-term survival after pancreaticoduodenectomy (PD) is not clear.MethodsThis is a retrospective analysis of prospectively maintained database of 141 patients with periampullary and pancreatic head adenocarcinoma operated between January 2001 and March 2019. Clinico-pathological records and follow-up data were retrieved and analyzed. Cumulative hazard was computed for comparing the survival between DM and non-DM.ResultsDM was present in 31/141 (21.9%) patients, while 16/31 (51.6%). were new-onset DM (NODM). Tumor size, lymphovascular & perineural invasion, type of surgery, lymph node positivity and R0 resection rate were comparable between diabetic and non-diabetic. There was no significant difference in postoperative pancreatic fistula, delayed gastric emptying, infectious complication, hospital stay and mortality between DM and nondiabetics. Patients with DM had worse survival at 3 years (OS: HR, 3.11 [1.43-6.76] p=0.004, DFS: HR, 2.61 [1.23-5.53] p=0.01) and 5 years (OS: HR, 3.32 [1.46-7.53] p=0.004, DFS: HR, 2.87 [1.29-6.41] p=0.009). On multivariate analysis, DM (3 year OS: HR, 2.61 [1.14-5.98] p=0.022, DFS: HR, 2.19; p=0.058) (5 year OS: HR, 2.55; p=0.04, DFS: HR, 2.25; p=0.068) and pylorus resecting surgery were significantly associated with worse survival at 3 and 5 years.ConclusionsPreoperative DM has no significant effect on postoperative course but has negative impact on 3-year and 5-year OS and DFS after PD for pancreatic and periampullary adenocarcinoma.