Intussusception in adults is uncommon, and it is rare in the descending colon because of its fixation to the retroperitoneum. We herein describe a case of intussusception caused by descending colon cancer. A 74-year-old man was admitted to our hospital for treatment of vomiting and abdominal pain. He had undergone chemotherapy for lymph node recurrence of stomach cancer for about 4 years. Computed tomography revealed a 'target mass' with a tumor in the descending colon. We diagnosed his illness as intussusception of a descending colon tumor and performed emergency laparotomy. Conservative resection was performed following anastomosis after reduction of the intussusception. The tumor was pathologically diagnosed as poorly differentiated adenocarcinoma with neuroendocrine features. To the best of our knowledge, this is the first report of an intussusception caused by descending colon cancer incidentally diagnosed during chemotherapy for stomach cancer recurrence.