BACKGROUND/AIM: To clarify the usefulness of intraoperative colonoscopy (CS) for preventing postoperative anastomotic leakage and bleeding in rectal cancer surgery. PATIENTS AND METHODS: The data of rectal cancer patients who underwent circular-stapled anastomosis from January 2008 to December 2016 were compared between 162 patients who received intraoperative CS (the CS group) and 23 patients who did not receive intraoperative CS (the non-CS group). RESULTS: Anastomotic leakage rate in the CS group (8.6%) was similar to that in the non-CS group (4.3%) (p=0.70). Postoperative anastomotic bleeding rate was also similar between the CS and non-CS groups (2.4% vs. 0%, p=0.50). Although a positive air leak test was observed in two patients in the CS group, no postoperative leakage developed by adding intraoperative treatment. CONCLUSION: Although intraoperative CS did not significantly reduce the incidence of postoperative anastomotic leakage or bleeding, it can be useful for certain cases.