This study investigated the relationship between the subjective outcome assessment and objective parameters after intravesical onabotulinumtoxinA injection in patients with overactive bladder (OAB). A total of 77 consecutive patients with urodynamically confirmed detrusor overactivity were treated with intravesical 100 U of onabotulinumtoxinA in 20 divided injections (5 U in 0.5 ml normal saline each) at different sites sparing the trigone. The primary end-point was the change in the Global Response Assessment (GRA) 3 months after treatment. All patients were monitored monthly after treatment for up to 6 months. Patients were divided into successful and failed treatment groups according to change in their GRA (≥2 and ≤1, respectively) at 3 months. The changes in voiding diary variables, Urgency Severity Score (USS), Overactive Bladder Symptom Score (OABSS), maximal bladder capacity (MBC), post-void residual (PVR) volume, and voiding efficiency (VE) were compared between groups at each time point. Overall, USS, OABSS, and MBC improved after treatment. Three months after BoNT-A injection, 49 (64%) patients reported an improvement in the GRA of 2 (n = 30) or 3 (n = 19). Patients with GRA ≥ 2 had significant improvements in OABSS at 3 months, and USS, OABSS, urgency urinary incontinence (UUI), and urgency episodes at 6 months compared with patients with GRA ≤ 1. No significant difference in MBC, PVR, or VE was noted between groups at 3 or 6 months. Subjectively successful treatment outcomes of intravesical onabotulinumtoxinA injection for OAB patients were associated with improvement in OAB symptoms but not increased bladder capacity. Neurourol. Urodynam. 36:338-343, 2017. © 2015 Wiley Periodicals, Inc.