BACKGROUND Mature ovarian teratomas account for 20% of all adnexal tumors and consist of mature elements from all 3 germ layers. Immature teratomas are much rarer, comprising only 3% of clinical cases. These tumors, which arise from primordial germ cells, can contain both differentiated and undifferentiated tissue, primarily neuroepithelium. It is very rare for a single patient to have both gonads affected, especially by 2 different types of teratomas. This report describes the case of a 30-year-old woman with a right ovarian mature cystic teratoma and a left ovarian immature teratoma. CASE REPORT This report discusses the case of a 30-year-old woman who presented with tumors on both ovaries. Both lesions were surgically removed and histologically analyzed. An immature teratoma was diagnosed on the left ovary and a mature one on the right one. The patient received chemotherapy, which was discontinued due to complications. Follow-up imaging revealed no recurrences. The patient remains under oncological care with regular follow-ups. CONCLUSIONS In cases of diagnostic uncertainty, computed tomography (CT) is recommended, as it provides detailed imaging of the tumor's structure. The most important element of diagnosing both mature and immature teratomas, providing a clear and indisputable diagnosis, is a histopathological examination. Unfortunately, these tumors do not usually cause specific symptoms. This report highlights the importance of thorough histological sampling and evaluation of ovarian tumors, including ovarian mature cystic teratoma, so that malignant elements are not missed and patients receive appropriate management.