Aim: Cranberries (Vaccinium macrocarpon) are traditionally used in prevention of urinary tract infections (UTIs). The authors' aim was to evaluate effects of a supplement containing cranberry extract, pumpkin seed extract, vitamin C, and vitamin B-2 on recurrent uncomplicated UTIs in women and their intestinal microbiota.Methods: A prospective, uncontrolled exploratory study was conducted in women with recurrent uncomplicated UTIs. The primary exploratory outcome was the number of UTIs in a 6-month prospective observation period compared with a 6-month retrospective period. Further outcomes included number of antibiotics, quality of life (SF-36), intestinal microbiota (assessed by 16S rRNA amplicon sequencing), and evaluation questions. Parameters were assessed at baseline and after 1, 2, and 7 months (start of intake of cranberry supplement after 1 month for 6 months). p-Values were calculated with the pairwise Wilcoxon signed-rank test for alpha diversity and permutational multivariate analysis of variance.Results: Twenty-three women (aged 52.7 +/- 12.4 years) were included in the study. Participants reported 2.2 +/- 0.8 UTIs (at baseline) in the previous 6 months. After 6 months of cranberry intake, participants reported a significant decrease to 0.5 +/- 0.9 UTIs (p < 0.001). Number of antibiotic therapies was also significantly (p < 0.001) reduced by 68% during 6 months of cranberry intake (0.14 +/- 0.35) when compared with 6 months retrospectively (1.14 +/- 0.71). The SF-36 physical component score increased from 44.9 +/- 5.5 at baseline to 45.7 +/- 4.6 at 7 months (p = 0.16). The SF-36 mental component score decreased slightly from the baseline value of 46.5 +/- 6.5 to 46.2 +/- 6.4 at 7 months (p = 0.74). No significant intragroup mean changes at genus, family, or species level for alpha and beta diversity within the intestinal microbiota were found. In the evaluation questions, participants rated the cranberry extract positively and considered it beneficial. The supplement intake was safe.Conclusions: This study shows that women with recurrent uncomplicated UTIs benefit from cranberry intake. Future larger clinical studies with further investigation of the mechanisms of action are required to determine the effects of cranberries on participants with uncomplicated UTIs.