Iatrogenic rectal diverticulum is an exceptionally rare complication following the Longo procedure (stapled hemorrhoidopexy), with only a handful of cases reported in the literature. This case is noteworthy due to its rarity, the diagnostic challenges it presents, and its therapeutic implications for patients undergoing stapled hemorrhoidopexy. Reporting this case aims to raise awareness among clinicians about this uncommon complication and contribute to the understanding of its clinical management. A 60-year-old woman underwent the Longo procedure in 2021 for symptomatic Grade III hemorrhoidal disease and rectocele. The initial surgery was successful, with no immediate postoperative complications. However, four years later, she presented with rectal discomfort but no other significant symptoms. Diagnostic evaluation, including colonoscopy and rectal ultrasonography, revealed a large diverticulum at the site of the previous stapled anastomosis, at five o'clock position. Surgical intervention was planned, involving resection of the diverticulum and primary repair of the rectal wall. Histopathological examination confirmed the presence of a true diverticulum involving all layers of the rectal wall. The patient recovered well postoperatively, with resolution of symptoms and no further complications at follow-up. This case highlights rectal diverticulum as a rare but significant late complication of the Longo procedure. It underscores the importance of considering this entity in patients with persistent or recurrent symptoms after stapled hemorrhoidopexy. Long-term follow-up and a high index of suspicion are essential for timely diagnosis and management. The case also emphasizes the need for further research to understand the underlying mechanisms, such as altered rectal wall mechanics or stapling-related tissue changes, and to optimize treatment strategies. Clinicians should be aware of this complication to improve patient outcomes and guide informed decision-making in the management of hemorrhoidal disease.