Abscess formation of the falciform ligament is incredibly rare and perplexing when encountered for the first time. It is reported to occur in the setting of cholecystitis and cholangitis, but the pathophysiology is poorly understood.In this case report, we present a 73-year-old man with falciform ligament abscess following cholangitis from an obstructive ampullary carcinoma. The patient was referred to the Royal Adelaide Hospital from a country hospital, with progressive jaundice, anorexia and nausea. Prior to transfer, he deteriorated with cholangitis, dehydration and renal failure. On arrival, his abdomen was exquisitely tender along the course of the falciform ligament. His blood tests revealed an elevated white cell count of 14.9 x 103/μl, bilirubin of 291μmol/l and creatinine of 347 μmol/l. His CA 19-9 was markedly elevated at 35,000 kU/l. A non-contrast computed tomography (CT) demonstrated gross biliary dilatation and a collection tracking along the path of the falciform ligament to the umbilicus.The patient was commenced on intravenous antibiotics and underwent an urgent endoscopic retrograde cholangiopancreatogram (ERCP) with sphincterotomy and biliary stent drainage. Cholangiogram revealed a grossly dilated biliary tree, with abrupt transition at the ampulla, which on biopsy confirmed an obstructing ampullary carcinoma. Following ERCP, his jaundice and abdominal tenderness resolved. He was optimized over 4 weeks for an elective pancreaticoduodenectomy.At operation, we found abscess transformation of the falciform ligament. Copious amounts of pus and necrotic material was drained. Part of the round ligament was resected along the undersurface of the liver. Histology showed that there was prominent histiocytic inflammation with granular acellular eosinophilic components. The patient recovered slowly but uneventfully.A contrast CT scan undertaken 2 weeks post-operatively (approximately 7 weeks after the initial CT) revealed left portal venous thrombosis, which was likely to be a delayed discovery and was managed conservatively.We present this patient’s operative images and radiographic findings, which may explain the pathophysiology behind this rare complication. We hypothesize that cholangitis, with secondary portal pyaemia and tracking via the paraumbilical veins, can cause infectious seeding of the falciform ligament, with consequent abscess formation.