Portal or superior mesenteric vein (PV-SMV) resection and reconstruction is sometimes required during pancreatic tumor resection. In patients requiring segmental venous resection with interposition grafting, the left renal vein (LRV) is an accessible autologous solution. However, long-term patency outcomes of the LRV as an interposition conduit in this setting have not been analyzed. We conducted a retrospective analysis of patients undergoing pancreatic resection with PV-SMV reconstruction using LRV between 2002 and 2022. The primary outcome was PV-SMV patency at last follow-up, assessed with postoperative CT scans and analyzed using Kaplan-Meier survival methods that account for variation in follow-up duration. Development of any postoperative acute kidney injury within 7 days of surgery and morbidity were secondary outcomes. The study cohort includes 65 patients who underwent LRV harvest; 60 (92%) ultimately underwent successful reconstruction with harvested LRV graft. Kaplan-Meier 2-year estimated patency rate of the LRV graft was 88%, with no cases of complete occlusion. Six (10%) patients experienced graft stenosis. Nine of 61 (15%) patients experienced grade II or III acute kidney injury, 6 of 9 returning to normal renal function before discharge. No difference in median serum creatinine was observed at baseline, 6 and 12 months from surgery. LRV remnant thrombosis was seen in 7 of 65 (11%) patients. Only 3 of 61 (5%) patients had persistent acute kidney injury caused by complications unrelated to LRV harvesting. Autologous LRV graft was a reliable conduit for segmental PV-SMV reconstruction, resulting in a high patency rate and marginal impact on renal function. LRV harvest is a safe and potentially ideal surgical option for PV-SMV reconstruction in pancreatic surgery.