INTRODUCTION AND HYPOTHESIS: Mindfulness-based stress reduction (MBSR) is a standardized meditation program that may be an effective therapy for interstitial cystitis/bladder pain syndrome (IC/BPS), a condition exacerbated by stress. The aims of this study were to explore whether MBSR improved IC/BPS symptoms and the feasibility/acceptability of MSBR among women with IC/BPS. METHODS: This randomized controlled trial included women with IC/BPS undergoing first- or second-line therapies. Women were randomized to continuation of usual care (UC) or an 8-week MBSR class + usual care (MBSR). Participants completed baseline and 8-week post-treatment questionnaires, including the O'Leary-Sant Symptom Problem Index (OSPI), the visual analog pain scale (VAS), the Short Form Health Survey (SF-12), the Female Sexual Function Index (FSFI), and the Pain Self-Efficacy Questionnaire (PSEQ). The Global Response Assessment (GRA) was completed post-treatment. Analyses were performed using Student's t test, Chi-squared, and MANOVA where appropriate. RESULTS: Eleven women were randomized to UC and 9 to MBSR, without differences in group characteristics. More MBSR participants' symptoms were improved on the GRA (7 out of 8 [87.5 %] vs 4 out of 11 [36.4 %], p = 0.03). The MBSR group showed greater improvement in the OSPI total (p = 0.0498) and problem scores (p = 0.036); the OSPI symptom score change did not differ. PSEQ scores improved in MBSR compared with UC (p = 0.035). VAS, SF-12, and FSFI change did not differ between groups. Eighty-six percent of MBSR participants felt more empowered to control symptoms, and all participants planned to continue MBSR. CONCLUSIONS: This trial provides initial evidence that MBSR is a promising adjunctive therapy for IC/BPS. Its benefit may arise from patients' empowerment and ability to cope with symptoms.