Purpose: This study investigated the long-term outcomes of patients treated with fenestrated and branched endovascular aneurysm repair (F-BEVAR) or open surgical repair (OSR) for complex abdominal aortic aneurysms (c-AAAs). Complex abdominal aortic aneurysms are defined as aneurysms that involve the renal or mesenteric arteries and extend up to the level of the celiac axis or diaphragmatic hiatus but do not extend into the thoracic aorta. This study compares with a propensity-score matching the outcome of these procedures from 2 high-volume aortic centers. Materials and Methods: All patients with c-AAAs undergoing repair at 2 centers between January 2010 and June 2016 were included. The long-term imaging follow-up consisted in a yearly computed tomography angiography (CTA) in the F-BEVAR group. Yearly abdominal ultrasound examination and 5-year CTA were performed in the OSR group. The primary endpoints were long-term mortality, aneurysm-related mortality, and chronic renal decline (CRD), defined as estimated glomerular filtration rate reduction to <60 mL/min/1.73 m2 or >20%/de novo dependence on permanent dialysis in patients with normal or abnormal preoperative renal function, respectively. Secondary endpoints included aortic-related reinterventions, target vessel occlusion, proximal aorta degeneration, access-related complications, graft infection, and the composite endpoint of clinical failure during follow-up. Results: After 1:1 propensity matching, 102 consecutive patients who underwent F-BEVAR and OSR, respectively, were included. The median follow-up was 67 months. There was no significant difference in long-term overall mortality (40.2% vs 36.3%; p=0.40) and aneurysm-related mortality (6.8% vs 5.8%; p=0.30), in the F-BEVAR and OSR groups, respectively. During follow-up, late renal function decline occurred in 27 (27.8%) versus 46 patients (47.4%) in the F-BEVAR and OSR groups, respectively (p<0.01). During follow-up, 23 reinterventions (23.5%) were performed in the F-BEVAR group, and 5 (5.1%) in the OSR group (p<0.01). Conclusions: No differences in overall and aneurysm-related mortality were observed. Chronic renal decline was significantly higher after OSR, while the reintervention rate was higher in the F-BEVAR group. These long-term results reflect the outcomes of a complex procedure performed by a single experienced operator in 2 high-volume centers, and followed with a strict surveillance imaging follow-up. Clinical Impact Nowadays, F-BEVAR and OSR are considered two established techniques for the treatment of c-AAA. However, long-term comparative outcomes are not well studied, and concerns may rise in terms of durability of the repair, risk of reinterventions and late chronic renal decline. The present study showed, with a median follow-up > 5 years, no differences in overall and aneurysm-related mortality. Chronic renal decline was significantly higher after OSR, while the reintervention rate was higher in the endovascular group. To achieve the best possible long-term outcomes, both techniques should be performed in high volume aortic centres, tailored to the patient, and with an adequate surveillance imaging.