As the muscular and connective tissue components of the vagina are estrogen responsive, clinicians may recommend vaginal estrogen to optimize tissues preoperatively and as a possible means to reduce prolapse recurrence, but long-term effects of perioperative intravaginal estrogen on surgical prolapse management are uncertain. This study aimed to compare the efficacy of perioperative vaginal estrogen vs placebo cream in reducing composite surgical treatment failure 36 months after native tissue transvaginal prolapse repair. This was an extended follow-up of a randomized superiority trial conducted at 3 tertiary US sites. Postmenopausal patients with bothersome anterior or apical vaginal prolapse were randomized 1:1 to 1-g conjugated estrogen cream (0.625 mg/g) or placebo, inserted vaginally twice weekly for ≥5 weeks preoperatively and continued twice weekly for 12 months postoperatively. All participants underwent vaginal hysterectomy (if the uterus was present) and standardized uterosacral or sacrospinous ligament suspension at the surgeon's discretion. The primary report's outcome was time to failure by 12 months postoperatively, defined by a composite outcome of objective prolapse of the anterior or posterior walls beyond the hymen or the vaginal apex descending below one-third the total vaginal length, subjective bulge symptoms, and/or retreatment. After 12 months, participants could choose to use-or not use-vaginal estrogen for atrophy symptom bother. The secondary outcomes included Pelvic Organ Prolapse Quantification points, subjective prolapse symptom severity using the Patient Global Impression of Severity and the Patient Global Impression of Improvement, and prolapse-specific subscales of the 20-Item Pelvic Floor Distress Inventory and the Pelvic Floor Impact Questionnaire-Short Form 7. Data were analyzed as intent to treat and "per protocol" (ie, ≥50% of expected cream use per medication diary). Of 206 postmenopausal patients, 199 were randomized, and 186 underwent surgery. Moreover, 164 postmenopausal patients (88.2%) provided 36-month data. The mean age was 65.0 years (standard deviation, 6.7). The characteristics were similar at baseline between the groups. Composite surgical failure rates were not significantly different between the estrogen group and the placebo group through 36 months, with model-estimated failure rates of 32.6% (95% confidence interval, 21.6%-42.0%) and 26.8% (95% confidence interval, 15.8%-36.3%), respectively (adjusted hazard ratio, 1.55; 95% confidence interval, 0.90-2.66; P=.11). The results were similar for the per-protocol analysis. Objective failures were more common than subjective failures, combined objective and subjective failures, or retreatment. Using the Patient Global Impression of Improvement, 75 of 80 estrogen participants (94%) and 72 of 76 placebo participants (95%) providing 36-month data reported that they were much or very much better 36 months after surgery (P>.99). These data included reports from 51 of 55 "surgical failures." Pelvic Organ Prolapse Quantification measurements, Patient Global Impression of Severity scores, and prolapse subscale scores of the 20-Item Pelvic Floor Distress Inventory and Pelvic Floor Impact Questionnaire-Short Form 7 all significantly improved for both the estrogen and placebo groups from baseline to 36 months postoperatively without differences between the groups. Of the 160 participants providing data on vaginal estrogen usage at 36 months postoperatively, 40 of 82 participants (49%) originally assigned to the estrogen group were using prescribed vaginal estrogen, and 47 of 78 participants (60%) assigned to the placebo group were using vaginal estrogen (P=.15). Adjunctive perioperative vaginal estrogen applied ≥5 weeks preoperatively and 12 months postoperatively did not improve surgical success rates 36 months after uterosacral or sacrospinous ligament suspension prolapse repair. Patient perception of improvement remained very high at 36 months.