Visceral pseudoaneurysms resulting from pancreatitis occur in approximately 10% of cases. The present report describes a left colic artery pseudoaneurysm from pancreatitis presenting with active duodenal bleeding. Based on the clinical and endoscopic demonstration of duodenal bleeding, celiac and superior mesenteric arteriograms were initially obtained, and their findings were negative. Repeat arteriography, including an inferior mesenteric artery injection, demonstrated a left colic pseudoaneurysm with rupture into the pancreatic duct and retrograde flow into the duodenum. Because of inconsistent diagnostic yields for arteriography performed for pancreatitis-related bleeding, the authors recommend disciplined interrogation of all three major mesenteric vessels, unbiased by initial endoscopic findings, to reduce false-negative examination results and empiric embolization.