Objective To compare the safety and efficacy of combined therapy using sildenafil and tamsulosin for management of acute urinary retention (AUR) with tamsulosin alone in patients with benign prostate hyperplasia (BPH). Materials and Methods 101 patients were enrolled in a randomized placebo-controlled study from June 2009 to April 2012. Patients presenting with an initial episode of spontaneous AUR underwent urethral catheterization and then prospectively randomized to receive tamsulosin 0.4mg plus sildenafil 50mg in group A and tamsulosin 0.4mg plus placebo in group B for three days. Urethral catheter was removed three days after medical treatment and patient’s ability to void assessed at the day after catheter removal and seven days later. Patients who voided successfully were followed at least for three months. Results Mean age of patients was 59.64 ± 3.84 years in group A and 60.56 ± 4.12 years in group B (p value = 0.92). Mean prostate volume and mean residual urine were comparable between both groups (p value = 0.74 and 0.42, respectively). Fifteen patients in group A (success rate: 70%) and nineteen patients in group B (success rate: 62.7%) had failed trial without catheter (TWOC) at 7th day following AUR (p value = 0.3). No significant difference was noted between both groups regarding the rate of repeated AUR at one month and three month follow-up period (p = 0.07 and p = 0.45, respectively). Conclusion It seems that combination therapy by using 5-phosphodiesterase inhibitor and tamsulosin has no significant advantages to improve urinary retention versus tamsulosin alone.