Background: Teratoma is a tumor comprised of three germinal layers classified as mature or immature in most cases. Most mature solid teratomas are benign but may turn malignant; therefore, complete resection is advised in these cases. They usually occur in women. Primary rectal teratomas are infrequent, and only a few cases have been described in the literature. Teratomas are the most common cystic that rise in the ovary, testicle, and retroperitoneum. They can also be solid and are better known as dermoid cysts. Case Presentation: We report a 34-year-old woman who were presented with intermittent constipation and diarrhea in Urmia Imam Khomeini Hospital in January 2020. After examination, a solid intra-rectal teratoma occurring mainly in the rectum was detected in this case. The patient underwent segmental colectomy and histology, which revealed squamous epithelium, fat cells, hair follicles, cartilaginous material, and granuloma suggestive of mature teratoma. Conclusion: The present case was a solid primary rectal teratoma, an uncommon disease with many misdiagnoses that can be differentiated from other diseases. In this case report, it is differentiated from irritable bowel syndrome (IBS).