Introduction: Acute urinary retention due to benign prostatic enlargement is one of the clinical complaints that patients refer to the emergency department. Selective α-blockers are used after urinary catheterization. Recently, the use of nitrate compounds has been shown to relieve bladder neck and to treat acute urinary retention. Objective: The aim of this study was to survey the addition of Isosorbide di nitrate to tamsulosin in the treatment of acute urinary retention in patients with benign prostatic hyperplasia. Methods: This is a randomized, double-blind placebo-controlled clinical trial. In all, 78 patients with benign prostatic hyperplasia-related acute urinary retention referred to the emergency department were divided into two groups and randomly assigned to receive either 0. 4 mg tamsulosin plus placebo or 0. 4 mg tamsulosin plus isosorbide dinitrate 40 mg extended-release tablets daily for 3 days. At the same first visit, the catheter was removed and the ability to void in same time and 1 month later was assessed in each group. Results: After catheter removal, 27 (67. 5%) patients in the tamsulosin plus placebo group and 31 (81. 6%) in the tamsulosin plus isosorbide dinitrate group voided successfully after 3 days (p = 0. 155). After 1 month, 20 (50. 0%) patients taking tamsulosin plus placebo and 23 (60. 5%) taking tamsulosin plus isosorbide dinitrate could void, yet indicating no significant difference (p = 0. 350). Conclusions: Addition of isosorbide dinitrate to α-blockers has advantage in improving benign prostatic hyperplasia-related acute urinary retention versus tamsulosin alone, although was not statistically significant.