Pancreaticoduodenectomy (PD) with vein resection is the only potentially curative option for patients with pancreatic ductal adenocarcinoma (PDAC) with venous involvement. The aim of our study was to assess the oncological prognostic significance of the different variables of venous involvement in patients undergoing PD for resectable and borderline-resectable with venous-only involvement (BR-V) PDAC. We performed a retrospective analysis of prospectively acquired data over a 10-year period. Of the 372 patients included, 105 (28%) required vein resection and vein wall involvement was identified in 37% of those. A multivariable analysis failed to identify the vein-related resection margins as independent predictors for OS, DFS or LR. Vein wall tumour involvement was an independent predictor of OS (risk x1.7-2) and DFS (risk x1.9-2.2) in all models, while it replaced overall surgical margin positivity as the only parameter independently predicting LR during an analysis of separate resection margins (risk x2.4). Vein wall tumour invasion may be a more reliable predictor of oncological outcomes compared to traditionally reported parameters. Future studies should focus on possible pre-operative investigations that could identify these cases and management pathways that could yield a survival benefit, such as the use of neoadjuvant treatments.