BACKGROUND: Primary ovarian carcinoid tumors are uncommon neuroendocrine neoplasms, most often arising within mature cystic teratomas. Preoperative diagnosis is difficult because their imaging features may overlap with those of malignant epithelial ovarian tumors. Management is particularly challenging in young patients who desire fertility preservation, as evidence is limited and largely based on case reports. CASE PRESENTATION: We report a 30-year-old nulligravid woman with a two-year history of primary infertility who presented with intermittent pelvic pain, menorrhagia, and a persistent enlarging right ovarian mass. Her ovarian reserve was favorable, and hysterosalpingography showed left proximal tubal obstruction with right tubal patency. Preoperative color Doppler transvaginal ultrasonography demonstrated a solid hypervascular right ovarian lesion classified as O-RADS 5, raising strong suspicion for malignancy. Primary laparotomy with staging was recommended, but the patient declined because of fertility-related concerns. She initially underwent laparoscopic right ovarian cystectomy/mass excision with preservation of the ovarian cortex. Frozen section suggested a neuroendocrine neoplasm. After final histopathological diagnosis and multidisciplinary review, embryo cryopreservation was performed, followed by definitive staging laparotomy including right oophorectomy, peritoneal washing cytology, omental biopsy, ipsilateral pelvic lymphadenectomy, and appendectomy. Histopathology and immunohistochemistry supported a well-differentiated primary ovarian insular carcinoid arising within a mature cystic teratoma, with findings most consistent with FIGO stage IA disease. Conventional postoperative imaging and gastrointestinal endoscopy did not identify an extragonadal primary tumor or metastasis. At 6 months, the patient remained disease-free. CONCLUSION: This case further illustrates that radiologically high-risk O-RADS 5 ovarian masses may ultimately represent rare, low-grade malignant neoplasms. Fertility-preserving management may be considered in carefully selected young patients after multidisciplinary evaluation, appropriate staging, and exclusion of metastatic disease. Longer follow-up is required before definitive oncologic conclusions can be made.