A six-year-old male orangutan, with thin appearance and poor hair coat, was constipated for many days. Its strong tenesmus caused rectal prolapse. On radiographs and abdominal palpation, the whole colon was impacted with hard fecal masses. Strongyloides were found in fecal examination. Enemas and luxatives were administered to remove feces under general anesthesia but failed. Celiotomy was performed and fecaliths removed by manual squeezing. The colon was fixed to dorsal abdominal wall using synthetic absorbable suture to prevent recurring rectal prolapse. After two weeks, intensive care, the animal recovered well, and the rectal prolapse has not happened again.