A 70s woman with a history of asthma and dyslipidemia underwent a robot-assisted abdominoperineal resection for rectal cancer. The ports were placed as per the method of Shizuoka Cancer Center and no intraoperative complications were observed. The colostomy was constructed in the left lower abdomen by the retroperitoneal route. The 12-mm port part was closed in 2 layers, the fascia and dermis, and the 8-mm port part was closed only in the dermis. The postoperative course was good; however, the patient vomited 10 days after surgery. Abdominal computed tomography revealed an incarcerated small intestine in the 8-mm port of the left abdomen, and it was diagnosed as port-site hernia incarceration. Emergency laparotomy hernia repair was performed on the day. A part of the 8-mm port was incised to 30-mm and the fascia dilatation to 30-mm was observed. The color tone of the incarcerated small intestine was good. Only adhesion peeling was performed, the small intestine was returned, and the fascia was closed. The postoperative course was uneventful and the patient was discharged 17 days after the second surgery. At the 1 year postoperative follow-up, recurrence of hernia or rectal cancer was not observed.