Aortocaval fistula is a rare complication arising from an abdominal aortic aneurysm. A typical feature observed during the arterial phase of contrast-enhanced CT scanning in such patients is simultaneous enhancement of the dilated inferior vena cava and aorta. Awareness of the specific radiologic features of aortocaval fistula may facilitate diagnosis when the condition is unsuspected clinically. We report a case of aortocaval fistula secondary to abdominal aortic aneurysm, and review the previous literature.