Rectosigmoid intussusception is a rare cause of bowel obstruction, accounting for only approximately 1%–2% of all bowel obstruction cases. While intussusception in adults typically occurs intra-abdominally and presents with signs and symptoms of intestinal obstruction, in rare cases, it can mimic a rectal prolapse if the intussusceptum protrudes through the anal canal. We herein report a case where an octogenarian woman presented with rectosigmoid intussusception through the anal canal, due to a sigmoid colon submucosal lipoma, who eventually required an open Hartmann’s procedure. Patients with rectal prolapse symptoms should be carefully examined to rule out intussuscepting masses as a differential, as it would necessitate earlier surgical intervention.