To explore the role of cholecalciferol for the prophylaxis against recurrent urinary tract infection (UTI) in patients with benign prostatic hyperplasia (BPH).Our randomized, uncontrolled prospective study included 389 naïve BPH patients with moderate/severe symptoms, consecutively. The patients were randomly allocated to two groups; group-A included 193 patients who received tamsulosin, while group-B included another 196 patients who received tamsulosin with cholecalciferol. The study population was followed up for 2 years after the start of the treatment. For all the patients enrolled, clinical evaluation, imaging studies (abdominal and trans-rectal ultrasonography), and laboratory investigations [including urinalysis, urine culture with antibiotic susceptibility testing for positive cultures and estimation of prostate-specific antigen (PSA) level] were provided.The incidence rate of recurrent UTI was 9% among the study population; it was significantly higher among group-A patients compared to those of group-B (13.5% vs. 4.6%, p 0.003, OR 2.7, 95% CI 1.5-4.3). Compared to patients of group-A, those of group-B developed a significantly lower level of PSA at the end of treatment period (0.16 ± 0.03 ng/mL vs. 0.27 ± 0.08 ng/mL, p 0.043, OR 1.9, 95% CI 1.2-6.8).Adjuvant cholecalciferol supplementation may be protective against recurrent UTI among patients with BPH receiving tamsulosin therapy without extra adverse effects.