AIMS: Urinary tract infection (UTI) is a common complication after pelvic floor surgery. Antibiotics as prophylaxis may reduce the prevalence of UTI's by 50%, but bacterial resistance may be a large disadvantage, necessitating the search for other possible prophylactic options. Recent research found a 50% reduction in the rate of UTI's with the use of cranberry capsules after elective gynecologic surgery, suggesting that cranberry capsules may serve as a good prophylaxis. The aim of this study was to assess whether perioperative cranberry prophylaxis reduces the risk of clinical overt UTI after elective pelvic floor surgery with indwelling catheter. METHODS: We conducted a single-center randomized, double-blind, placebo-controlled trial. Women were given cranberry capsules twice daily or identical placebo for 6 weeks, starting the day before surgery. The main endpoint of the trial was the incidence of UTI within 6 weeks after surgery, defined as clinical diagnosis and treatment of UTI by the medical doctor. Analyses were performed with the intention to treat. RESULTS: Two hundred ten participants were included, 105 in each arm. There was no significant difference in the prevalence of UTI between the cranberry arm (n = 13, 12.4%) and the placebo arm (n = 21, 20.0%; P = .13), but the prevalence in both arms was lower than anticipated. CONCLUSIONS: This trial shows no beneficial effect of adequately dosed cranberry prophylaxis in women undergoing pelvic floor surgery, although such effect cannot be ruled out in settings with a higher prevalence of UTI's.