Superior mesenteric artery and pancreaticoduodenal artery aneurysms are rare. Agenesis of the celiac axis has only been reported four times. The reported etiologies of superior mesenteric artery and branch artery aneurysms include infection, atherosclerosis, inflammatory processes such as pancreatitis, dissection, collagen vascular disorders, polyarteritis nodosa, and trauma. We report an aneurysm of the superior mesenteric artery (SMA) branch, the inferior pancreaticoduodenal artery, arising in a patient with congenital absence of the celiac trunk. The patient presented with intermittent left upper quadrant pain without weight loss or change in bowel habits. The aneurysm was identified on abdominal computed tomography scan with angiographic confirmation of the aberrant anatomy. The patient was treated by aneurysmectomy and pancreaticoduodenal artery reconstruction with an interposition vein graft from the SMA. The patient recovered without complications and is asymptomatic with a patent vein graft 2 years after operation.