Simple prostatectomy remains the gold standard treatment for patients with severe lower urinary tract symptoms (LUTS) and patients with enlarged prostate. Obesity, defined as a body mass index over 30kg/m2 by the World Health Organization (WHO), is associated with some perioperative complications. This study aims to investigate the effects of obesity on the outcomes of open simple prostatectomy.The study includes 72 patients that underwent open simple prostatectomy. We compared the treatment outcomes of 49 patients with a body mass index (BMI)<30kg/m2 and 16 patients with a BMI>30kg/m2. We compared t he two groups in terms of change in International Prostate Symptom Score (IPSS), change in uroflowmetry maximum flow rate (Qmax), operation time, intraoperative blood loss, transfusion requirements.The median of change in IPSS scores was 16(11-30) for the group where BMI<30kg/m2 and 15.5(10-20) for the group where BMI>30kg/m2. This difference was not statistically significant (p=0.383). The mean duration of operation was 90.61±17.45 minutes for patients with BMI<30kg/m2 and 121.87±18.78 minutes for patients with a BMI>30kg/m2. The difference between the two groups was statistically significant (p<0.001). The median of blood loss was 450(200 -700) cc for the BMI<30kg/m2 group and 725 (550-850) cc for the BMI>30kg/m2 group, and this difference was statistically significant (p<0.001). However, the blood transfusion requirements of the two groups were statistically similar (p=0.885).Open simple prostatectomy is very important technic in the treatment of BPH patients with enlarged prostates. Despite obesity is associated with a prolonged operation and increased transfusion rates in open simple prostatectomy, it can still be considered a safe treatment method.