Background: Transurethral resection of prostate (TURP) is the gold standard in the surgical treatment of symptomatic benign prostatic hyperplasia (BPH). Blood loss is one of the most common complications of TURP. Objective: To evaluate the effect of preoperative dutasteride on bleeding related to TURP in patients with BPH. Materials and Methods: This prospective interventional study was done in the department of urology, Dhaka Medical College Hospital, Dhaka, Bangladesh during the period of July 2016 to June 2017. A total of 70 cases of BPH planned for TURP were included in this study according to the statistical calculation. Patients were randomly allocated to control group A (TURP without dutasteride) and dutasteride group B (TURP with dutasteride). Each group consisted of 35 patients. Group B patients were treated with dutasteride 0.5 mg/day for 4 weeks before TURP. The main outcome of blood loss was evaluated in terms of reduction in serum hemoglobin (Hb) and hematocrit (Hct) levels, which were measured before and 24 hours after surgery. Data were analyzed and compared by statistical tests. Results: Comparison of outcome between groups shows that there was a significant difference in term of pre-post operative change of hemoglobin and hematocrit levels in the control group A compared to the dutasteride group B (Hb = 2.96 ± 0.80 gm/dl vs. 1.81 ± 0.71 gm/dl, respectively, p = 0.001; Hct = 11.20% ± 2.12% vs. 6.07% ± 2.02%, respectively, p = 0.02