Iliac venous aneurysms are rare vascular abnormalities that may be manifested by abdominal masses, pelvic tenderness, or hypovolemia and may lead to rupture, thrombosis, pulmonary embolism, paradoxical embolism, or death. Inferior vena cava agenesis, like venous aneurysm, is an uncommon condition that may present with deep venous thrombosis. This report describes a patient with inferior vena cava agenesis and iliac venous aneurysm rupture treated with emergent iliocaval reconstruction and endovascular stent graft placement.