Background: Epithelial tumors are the most common subgroup and are seen in 60-70% of all ovarian tumors. Serous cystadenoma and mucinous cystadenoma are the most common be-nign epithelial tumors. Serous cystadenomas are ovarian tumors with the highest bilateral inci-dence. The coexistence of tumors with different histopathology in the ovaries is extremely rare and has only been reported in a few cases in the literature. We present a case of bilateral ovarian tumor that was diagnosed as serous and mucinous cystadenoma after laparoscopic surgery. Case Report: A 45-year-old female patient was admitted to our center with swelling in the pelvic region and pain in the left lumbar region. US imaging showed a cystic lesion in the right adnexal area, 4x2 cm in size, well-circumscribed, containing a few thin septa, and a low echo fluid content. A cystic lesion with 6x4cm sized multilocular, well-circumscribed, slightly high echo fluid content was observed in the left adnexal area. On CT, a complex cystic lesion measuring 6x4cm was observed in the left adnexal area, pushing the left ureter laterally and causing the hydroureter. In addi-tion, a 4x2 cm cystic lesion was observed in the right adnexal area and hydroureter was observed on the right side proximal to this lesion. Both lesions were removed by surgery. On histopathologic examination, the left-sided cystic lesion was diagnosed as mucinous cystadenoma, and the right-sid-ed cystic lesion was diagnosed as serous cystadenoma. Conclusion: The coexistence of different ovarian tumor subtypes is rare. In this article, we present-ed a case in which serous and mucinous cystadenoma lesions were seen together for the fourth time in the literature, according to our knowledge.