RATIONALE: Carcinoid tumors arising from mature cystic teratomas of the ovary (MCTO) are exceptionally rare and often misdiagnosed as benign teratomas on imaging studies, which can lead to delayed or inappropriate treatment. The purpose of this study is to raise awareness of this rare condition by presenting a case of a carcinoid tumor originating from MCTO, highlighting its unique imaging features and clinical presentation, and discussing the importance of accurate preoperative diagnosis. PATIENT CONCERNS: A 59-year-old woman was admitted to the hospital following an ultrasound physical examination that revealed an anterior uterine parenchymal mass. She exhibited no obvious abnormal clinical symptoms. DIAGNOSIS: CT and MRI of the pelvis revealed a cystic-solid soft tissue mass with small calcified foci and a significant cystic fatty component. There was a marked enhancement of the solid component in the pelvis off to the right, leading to the consideration of a teratoma. INTERVENTIONS: The final clinical preoperative diagnosis was an ovarian teratoma. Pelvic tumor resection was performed after the exclusion of contraindications to surgery. Postoperative pathology revealed a carcinoid tumor arising from MCTO. LIMITATIONS: This study is limited by the fact that it reports a single case, which makes it difficult to generalize the findings to a larger population. Additionally, the rarity of this condition means that there is limited literature available for comparison, which could provide a broader understanding of the potential challenges in diagnosing similar cases. The retrospective nature of the case also restricts the ability to conduct a more extensive analysis of potential risk factors. OUTCOMES: The patient did not receive adjuvant therapy post-surgery. During the 36-month follow-up period, the tumor showed no signs of recurrence or metastasis. The follow-up was concluded without further complications, indicating a favorable outcome. LESSONS: Mature cystic teratoma is a common ovarian tumor, but its association with carcinoid tumors is very rare and prone to preoperative misdiagnosis. The imaging presentation of this case is characteristic and has significant diagnostic implications for this disease.