The effect of transurethral resection of the prostate (TURP) on erectile function is still controversial, and available evidence is conflicting. One of the possible mechanisms of post-TURP erectile dysfunction (ED) is direct thermal injury to the erectile nerves. The aim of this study was to investigate the effect of TURP on erectile function. Fifty patients undergoing TURP for obstructive benign prostatic hyperplasia (HBP) were prospectively included in the study, and 50 age-matched patients undergoing transurethral resection of the superficial bladder tumor were also prospectively included as a control group. All patients completed the international index of erectile function (IIEF-15), the international prostatic symptom score (IPSS) and the Hospital Anxiety and Depression Scale at inclusion in the study and then at the 3-and 6-month follow-up evaluation. Capsular perforations during TURP were prospectively reported by the operating surgeon. There was a significant improvement of erectile function in the TURP group despite the onset of ejaculation disorders in 70% of the patients. Improvement of erectile function was also found in the subgroup of patients with capsular perforation during TURP. Comparison with the control group showed that at preoperative evaluation, patients in the TURP group had more severe urinary symptoms and worse erectile function than did those of the control group. At the postoperative period, the IPSS score became comparable in the two groups, with major improvement of erectile function in the TURP group. We concluded that TURP improved erectile function in HBP patients with severe urinary symptoms. This improvement of erectile function was observed even in case of capsular perforation.