A 66-year-old man presenting with melena was diagnosed with rectosigmoid cancer and underwent laparoscopic high anterior resection. Intraoperative findings showed that the descending colon did not adhere to the retroperitoneum and was largely displaced inward, and the descending and sigmoid colon extensively and strongly adhered to the small intestinal mesentery, as predicted prior to surgery. The patient was diagnosed with persistent descending mesocolon(PDM). The first sigmoid artery diverged from the left colonic artery; however, ligation of supplying arteries under laparoscopy was perceived as a risk for marginal artery injury due to the shortening of the mesentery by PDM. Therefore, the sigmoid artery and inferior mesenteric vein were ligated directly from the umbilical wound. No postoperative complications were observed, and the patient was discharged 9 days after the surgery. Although PDM has not been defined, it has been reported that preoperative prediction is possible depending on the positional relationship between the descending colon and the left kidney. In this case, we performed the surgery after taking into consideration the anatomical features assessed preoperatively, leading to a safe operation.