Transitional cell carcinoma of the ovary (TCC-O) is a less common type of malignant surface epithelial-stromal tumor of the ovary, still with uncertain incidence. Histologically, TCC-O resembles urothelial carcinoma of the urinary system, and by definition does not contain a Brenner tumor component. TCC-O may not be a bona fide urothelial neoplasm, however, but rather a lesion of the Müllerian type derived from the ovarian surface epithelium. This notion is supported by the existence of mixed tumors consisting of TCC-O and other histological types of ovarian carcinoma, as well as the observation that TCC-O has a Müllerian type but not a urothelial-like immunohistochemical profile. Besides metastatic urothelial carcinoma of the urinary tract, the other types of ovarian carcinoma, as well as sex cord-stromal tumors such as adult granulosa cell tumors, have to be considered in the differential diagnosis of TCC-O. A recent analysis of a large series of advanced ovarian carcinomas treated by radical surgery and postoperative chemotherapy confirms studies that had suggested that TCC-O has a better prognosis (with current treatment) than that of the other histological types of ovarian carcinoma. Further studies applying standardized histopathological criteria are needed to clarify the true incidence and behavior of TCC-O. In addition, it is important to study the biological and molecular background of this apparently less aggressive phenotype.