Introduction and Hypothesis <p>This study was aimed at evaluating the therapeutic effects of a modified intravesical botulinum toxin injection technique (fewer injection sites under local anesthesia), in comparison with the conventional technique for patients with idiopathic detrusor overactivity, considering the urodynamic parameters.</p> Methods <p>In this double-blinded randomized clinical trial, 78 adult females with idiopathic detrusor overactivity were divided into two groups: conventional and modified groups. In the conventional method, patients received intradetrusor botulinum toxin injection at 20 sites under general or spinal anesthesia in a trigone-sparing fashion. In the modified group, injections were performed at five intradetrusor sites beyond the trigone, using local anesthetics. The primary end point was the comparison of urodynamic parameters in both groups following the procedure. The secondary endpoints were assessing the safety and tolerability of the modified method compared with the conventional method.</p> Results <p>There were no significant differences between the two treatment groups in terms of urodynamic parameters before the intervention (<i>p</i> &gt; 0.05). After the intervention, no significant differences in urodynamic parameters were observed between the two treatment methods. All patients in the modified-method group could tolerate the procedure well.</p> Conclusion <p>The innovation of reducing the number of injection sites and concurrently using local anesthetics was shown to be as effective as the conventional method in terms of improving urodynamic parameters, tolerability, and safety in patients with idiopathic detrusor overactivity.</p>