Aims: Patients often experience adverse events (AEs) after intravesical onabotulinumtoxinA (BoNT-A) treatment for overactive bladder refractory to antimuscarinic agents. We investigated the prevalence and predictive factors of AEs in such patients. Methods: A total of 290 patients underwent intravesical BoNT-A(100 U) suburothelial injection. The age, gender, overactive bladder subtypes, medical co-morbidities, and neurological diseases of the patients were recorded. The maximum flow rate (Q(max)), voided volume, post-void residual (PVR) volume, and voiding efficiency (VE) at baseline were analyzed to identify adverse events within 3 months after treatment. Results: Acute urinary retention (AUR) developed in 24 patients (8.3%), and urinary tract infection (UTI) occurred in 44 (15.2%) within 3 months of treatment. Large PVR volume (>200ml) occurred in 81 (27.9%), 68 (24.3%), and 49 (18.4%) patients 1, 3, and 6 months after treatment, respectively. AUR developed significantly more often in men, patients>61 years old, those with a baseline Q(max)= 100ml, and VE= 100ml had a greater incidence of UTI. Age >61 years, low Q(max), low voiding efficiency, and large PVR at baseline were also risk factors for adverse events. Conclusion: AUR, UTI, and large PVR volume are common AEs after BoNT-A treatment. Patients with overactive bladders that are at risk of developing AEs after BoNT-A injection should be informed of the possible AEs. (C) 2015 Wiley Periodicals, Inc.