Background: Unruptured intracranial aneurysms (UIAs) are treated using endovascular treatment or microsurgical clipping. The safety and efficacy of treatments have not been compared in a randomized trial. Methods: We randomly allocated clipping or coiling to patients with 3-25mm UIAs judged treatable both ways. The primary outcome was treatment failure, defined as: initial failure of aneurysm treatment, intracranial hemorrhage or residual aneurysm on one year imaging. Secondary outcomes included neurological deficits following treatment, hospitalization >5 days, overall morbidity and mortality and angiographic results at one year. Results: 136 patients were enrolled from 2010 through 2016 and 134 patients were treated. The one-year primary outcome, available for 104 patients, was reached in 5/48 (10.4% (4.5%-22.2%)) patients allocated surgical clipping, and 10/56 (17.9% (10.0%-29.8%)) patients allocated endovascular coiling (OR: 0.54 (0.13, 1.90), P=0.40). Morbidity and mortality (mRS>2) at one year occurred in 2/48 (4.2% (1.2%-14.0%)) and 2/56 (3.6% (1.0%-12.1%)) patients allocated clipping and coiling respectively. New neurological deficits (15/65 vs 6/69; OR: 3.12 (1.05, 10.57), P=0.031), and hospitalizations beyond 5 days (30/65 vs 6/69; OR: 8.85 (3.22,28.59), P=0.0001) were more frequent after clipping. Conclusions: Surgical clipping led to greater initial treatment-related morbidity than endovascular coiling. At one year, the superior efficacy of clipping remains unproven and in need of randomized evidence.