Elective stent graft repair of iliac aneurysm is successful and safe. There are, however, few published data on stent grafting unstable patients with acute iliac aneurysm rupture. Iliac diameter mismatch can also present a challenge to emergency endovascular treatment. We report the treatment of an unstable patient with iliac aneurysm rupture and diameter mismatch using a percutaneous balloon-expandable polytetrafluoroethylene (PTFE) stent graft. Outcomes were satisfactory up to 12-month follow-up. Treatment of iliac aneurysm rupture using a balloon-expandable stent graft can be successful in selected patients. A percutaneous approach and targeted stent graft postdilatation enable prompt repair in the presence of diameter mismatch, facilitating emergency therapy.