Background Vascular complications, most commonly arterial or venous thrombosis, are one of the most common causes of early graft loss after pancreas transplantation. However, only a few cases of pseudoaneurysm formation have been reported. Case report This case report is unique for the presentation of pancreatic graft pseudoaneurysm with a sentinel retroperitoneal bleed as well as the failure to achieve diagnosis by ultrasound or standard cut CT scanning. The case emphasizes the importance of clinical suspicion and the need for dedicated fine-cut CT angiography or standard percutaneous angiography for diagnosis. The site of the anastomosis precluded minimally invasive treatment options and open repair with graft salvage was accomplished with minimal morbidity. Conclusions Although pseudoaneurysm after pancreas transplantation is uncommon, unexplained post-operative bleeding, even in the stable patient, should raise the suspicion of a sentinel bleeding event necessitating urgent angiography. Rapid diagnosis and treatment can prevent potential life- and graft-threatening rebleeding. The choice between minimally invasive and open surgical repair should be individualized depending on the site of the lesion.