Vascular reconstruction can facilitate pancreas tumor resection, but optimal methods of reconstruction are not well studied. We analyzed our results for portal vein reconstruction (PVR) for pancreatic resection and determinants of postoperative patency. We identified 173 patients with PVR in a prospective database of 6522 patients who underwent pancreatic resection at our hospital from 1970 to 2014. A total of 128 patients had >6 months follow-up with computed tomography imaging. Preoperative, intraoperative, and postoperative factors were recorded. Patients with and without postoperative PVR thrombosis were compared using univariate, multivariate, and receiver-operating characteristic curve analyses. Patient survival was 100% at 1 month, 95% at 6 months, 83% at 1 year, and 54% on overall median follow-up of 194 days. Median survival was 14 ± 26 months. Eighty-two percent of PVRs were performed with a primary repair, 8.5% with interposition vein, 5.5% with interposition prosthetic graft, and 4% with patch. PVR patency was 100% at 1 day, 98% at 1 month, 91% at 6 months, and 83% at 1 year. Patients with PVR thrombosis were not significantly different from patients with a patent PVR in age, survival, preoperative comorbidities, tumor characteristics, perioperative blood loss or transfusion, or postoperative complications. They were more likely to have preoperative chemotherapy (53% vs 9%, P = .0001), radiation (35% vs 2%, P = .0001), prolonged operative time (610 ± 91 vs 423 ± 188 minutes, P = .0001), and develop postoperative ascites (76% vs 22%, P = .0001). The number of patients who developed ascites in the setting of tumor recurrence did not differ among those with thrombosed and patent PVR (38% vs 50%, P = .7). Patients with PVR thrombosis were more likely to have prosthetic graft placement than patients with a patent PVR (18% vs 2.7%; odds ratio [OR], 7.7; 95% confidence interval [CI], 1.4-42, P = .03). PVR patency at 6 months was significantly lower for graft reconstruction (0%) compared with primary repair (95%, P = .0004) and vein reconstruction (91%, P = .04). On multivariate analysis, operative time (OR, 1.01; 95% CI, 1.01-1.02) and prosthetic graft placement (OR, 8.12; 95% CI, 1.1-74) were independent predictors of PVR thrombosis (C statistic = 0.88). Long operative times and use of prosthetic grafts for reconstruction are risk factors for postoperative portal vein thrombosis. Primary repair and vein interposition should be preferentially used for PVR in the setting of pancreatic resection.