PURPOSE: To evaluate the technical feasibility and clinical outcomes of endovascular treatment for internal iliac artery (IIA) aneurysms. MATERIAL AND METHODS: This was a retrospective analysis of 25 patients with 32 IIA aneurysms (mean diameter: 39.1 +/- 12.6 mm) who underwent endovascular treatment over a 10-year period, and were available for follow-up. Univariate analysis was used to determine the association between variables (including aortoiliac involvement and technique) and outcome. RESULTS: The IIA inflow was covered with an iliac stent graft (N = 29) or embolized with a plug (N = 3). The IIA outflow was embolized in all but one case in which there was thrombotic occlusion of outflow branches. Outflow embolization using plugs or coils was performed in the distal IIA or anterior/posterior trunks in 9 cases and distal IIA branches in 22 cases. During a mean follow-up period of 39.9 months, 31.2% of aneurysms demonstrated endoleak and 12.5% demonstrated enlargement. Univariate analysis revealed that endoleak was associated with technical failure (p = 0.01) and that endoleak rate was higher in patients who underwent distal IIA branch embolization (p = 0.03). No variable was associated with sac expansion. Major complication occurred in one patient who died from aneurysm rupture. Minor complications were reported in six patients who developed femoral pseudoaneurysm (N = 2, 8%), buttock claudication (N = 3, 12%), and limb graft occlusion (N = 1, 4%). CONCLUSION: Endovascular treatment of IIA aneurysms effectively prevents sac expansion. Endoleak was more frequently observed in cases of technical failure and those in which distal IIA branches were embolized. LEVEL OF EVIDENCE: Level 3b, retrospective cohort study.