Aim: In this randomized prospective clinical study, we aimed to evaluate the effect of mechanical bowel preparation (MBP) before Milligan-Morgan hemorrhoidectomy on intraoperative procedures and postoperative complication rates to determine whether MBP is adventageous or not before elective anorectal surgeries. Methods: Forty patients who had internal grade III or IV hemorrhoidal disease and who would underwent open hemorrhoidectomy were randomized into two groups: non-MBP group (female:male, 11:9; mean age, 33.8±9.57 years) that would not receive MBP before the surgery, and MBP group (female:male, 12:8; mean age, 34.7±11.37 years) that would be given one Fleet enema on the morning of Milligan-Morgan hemorrhoidectomy. Intraoperative variables and postoperative complications were compared between two groups. Results: MPB had no effect on both intraoperative and postoperative variables, such as operating time, intraoperative bleeding, visual analogue scale (VAS) score for the comfort of the surgeon during operation, the presence of stool or enema remnants in anal canal, the presence of mucosal edema of the anal canal intraoperatively, the rates of postoperative bleeding and infection, VAS score for the pain on third day postoperatively, time to first stool after the operation, VAS score for the pain during first stool after the operation, and number of analgesics during one week postoperatively (P>0.05 for all). Conclusion: MBP performed before surgery does not provide introperative or postoperative benefit for Milligan-Morgan hemorrhoidectomy, thus MBP is not necessary before elective anorectal surgeries.