Background The rate of thromboembolic events (TEEs) associated with endovascular treatment (EVT) of intracranial aneurysms is not reported uniformly in the literature due to the various ways that are used to evaluate them. Analysis of Thromboembolic Complications after Endovascular Treatment of Unruptured Intracranial Aneurysms study (ACET) is a prospective, multicenter study, which analyzes the rate of TEEs using diffusion-weighted imaging (DWI) magnetic resonance imaging (MRI) in patients treated for unruptured aneurysms with different endovascular techniques. Methods Patients were prospectively included in six French centers. Postoperative DWI-MRI was performed within 72 hours post-procedure and independently evaluated. Univariate and multivariate analyses were conducted to determine factors associated with the occurrence of DWI lesions. Results Of the 233 included patients (54.5±11.2 years, 162 women, (69.5%)), 226 were effectively treated by EVT (coiling: 90 patients, 39.8%; balloon-assisted coiling (BAC): 62, 27.4%; stent-assisted coiling (SAC): 10, 4.4%; flow diversion (FD): 21, 9.3%; intrasaccular flow disruption (ISFD): 43, 19.0%) and had a postoperative MRI showing DWI lesions in 133 patients (58.8%). Univariate and multivariate analyses show the rate of patients with DWI lesions to be significantly higher with BAC (75.8%, P=0.001), SAC (90.0%, P=0.02), and FD (95.2%, P=0.001) compared with coiling alone (41.1%). Conclusions The rate of DWI lesions after EVT of unruptured aneurysms is primarily influenced by the EVT technique used. Techniques using transient (BAC) or permanent (SAC and FD) device placement in the parent artery are associated with a higher rate of DWI lesions. Trial registration number ACET: Unique identifier: NCT02862756 .