Retrorectal tumors are a rare group of tumors that can be of benign or malignant origin, the differential diagnosis concerns all retrorectal tumors. We report a case of a huge retrorectal cystic hamartoma in which surgical excision was performed. A 58 years-old female presented with a low back pain and constipation. Digital rectal examination found a renitent cystic mass compressing the posterior wall of the rectum. Colonoscopy showed a tumor compressing the rectum. Magnetic resonance imaging (MRI) scan showed a presacral cystic formation. Surgical resection using laparotomy was performed. The patient made a full recovery and was released eight days after the surgery. Histological examination of the mass revealed a retrorectal cystic hamartoma.