Iliac arteriovenous fistula is a rare but severe complication of iliac artery aneurysm. We present a case of iliac arteriovenous fistula concomitant with iliac artery aneurysm, which was preoperatively diagnosed by ultrasonography (USG) and successfully treated with emergent surgery. An 84-year-old female admitted to our hospital complaining of a sudden onset of right leg edema and dyspnea. Physical examination revealed pansystolic murmur at the right inguinal region. A chest X-ray showed enhanced pulmonary vascular shadow and bilateral pleural effusion with cardiomegaly. USG of the right lower abdomen revealed an arteriovenous fistula between the right iliac artery and vein concomitant with the iliac artery aneurysm. An emergent surgery was performed, and the fistula was directly closed within the aneurysm. To reduce bleeding through the fistula during surgery, we placed fingers inside the aneurysm and compressed the iliac vein just after the aneurysmal sac was opened. The postoperative course was satisfactory.