Objective <p>This study aimed to evaluate the efficacy and safety of pressure- and volume-controlled balloon dilation in the treatment of interstitial cystitis/bladder pain syndrome (IC/BPS) and to compare it with traditional bladder hydrodistension to explore a superior therapeutic approach.</p> Methods <p>A prospective randomised-controlled trial was conducted, enrolling 50 women with IC/BPS aged 52–77&#xa0;years, treated between July 2013 and June 2023. Patients were randomly assigned to a pressure- and volume-controlled balloon dilation group (experimental group, <i>n</i> = 25) or a traditional bladder hydrodistension group (control group, <i>n</i> = 25). The primary outcome measures included interstitial cystitis symptom index and interstitial cystitis problem index (ICSI/ICPI) scores, pelvic pain and urinary frequency (PUF) scores, bladder capacity, nocturnal urination frequency, maximum voided volume, and postoperative complications (bleeding and bladder rupture). Statistical analyses were performed using t tests, Wilcoxon rank-sum tests, and Chi-square tests, with <i>P</i> &lt; 0.05 indicating statistical significance.</p> Results <p>At 6&#xa0;months post-treatment, the experimental group showed significantly lower ICSI/ICPI scores than the control group (<i>P</i> &lt; 0.05). The experimental group also exhibited significantly lower PUF scores at all time points (<i>P</i> &lt; 0.05). Under non-anaesthetic conditions, the experimental group demonstrated significantly greater bladder capacity (<i>P</i> &lt; 0.05), whereas no significant difference was observed under anaesthetic conditions (P &gt; 0.05). The experimental group experienced significantly fewer episodes of nocturnal urination from 2&#xa0;weeks to 6&#xa0;months post-treatment (<i>P</i> &lt; 0.05).</p> Conclusion <p>Pressure- and volume-controlled balloon dilation demonstrated superior efficacy in alleviating IC/BPS symptoms and improving bladder function compared with traditional hydrodistension. Additionally, it was associated with a lower complication rate, offering a safer and more effective therapeutic option for patients with IC/BPS.</p> Clinical trial registration <p>ID:ISRCTN25030604, <a href="https://www.isrctn.com/ISRCTN25030604">https://www.isrctn.com/ISRCTN25030604</a></p>