The short- and mid-term outcomes of endovascular aortic aneurysm repair have made it a standard treatment of abdominal aortic aneurysms. However, newer generation devices have yet to demonstrate improved long-term rates for complications, reinterventions, and survival. The TREO stent graft is a latest generation device and was evaluated for approval in the United States. In a multicenter, nonrandomized, investigational device exemption clinical trial, we assessed the safety and effectiveness of the TREO device, with core laboratory assessment of the imaging studies and an independent adjudication of safety. The primary effectiveness endpoint was successful aneurysm treatment at 1 year. The primary safety endpoint was the incidence of major adverse events (MAE) at 30 days. A total of 150 patients (132 men; 88.0%) with infrarenal abdominal aortic (87.3%) or aortoiliac (12.7%) aneurysms were enrolled. The data were normally distributed. The mean age was 71.7 ± 7.4 years. The MAE incidence at 30 days was 0.7%. One subject experienced two MAE: myocardial infarction and procedural blood loss of 1000 mL. The proportion of successful aneurysm treatment at 1 year was 93.1%. Longer term follow-up continues, with no aneurysm-related mortality at the latest follow-up. At 3 years, the cumulative all-cause mortality and incidence of type I and type III endoleaks was 10.7% (n = 16), 2.7% (n = 4), and 0% (n = 0), respectively. In addition, aneurysm sac shrinkage >5 mm at 3 years had occurred in 54.3% of patients, and 9.3% had required a secondary intervention (n = 14). The safety and effectiveness of endovascular repair of abdominal aneurysms with TREO were demonstrated, with 93.1% successful aneurysm treatment at 1 year and aneurysm sac shrinkage >5 mm at 3 years in 54.3% of patients. Long-term follow-up continues to determine whether these favorable outcomes will be sustained. Copyright © 2020. Published by Elsevier Inc.