Full-thickness rectal prolapse occurs when the rectum invaginates into the anal canal and beyond the anal sphincters. It is estimated to occur in 2.5 per 100,000 people, and most commonly affects women, particularly elderly women with other pelvic floor disorders. The only definitive treatment for rectal prolapse is surgery. In this case, we present an 80-year-old female with full-thickness rectal prolapse who underwent Altemeier proctosigmoidectomy. The redundant rectum is delivered and then excised through a transanal approach, and the proximal colon is sutured to the distal end of the rectum.