Purpose: To investigate the incidence and survival outcomes of ovarian carcinosarcoma compared to those of epithelial ovarian cancer. Methods: Data on ovarian carcinosarcoma patients (n = 458) and epithelial ovarian cancer patients (n = 30,639) between 1999 and 2018 were obtained from the Korea Central Cancer Registry, and their respective agestandardized incidence rate (ASR) and relative survival rate were calculated and compared. Results: Based on the ASR, the incidence of epithelial ovarian cancer was 4.504 per 100,000 women, while that of primary ovarian sarcoma was 0.064 per 100,000 women. The ASR ratio was 70.375 without significant change of ASR during the study period. Ovarian carcinosarcoma had a worse survival curve compared with epithelial ovarian cancer, and the difference was statistically significant (median overall survival 39 months vs. 110 months; p-value < 0.0001). Among the ovarian carcinosarcomas, patients of localized stages showed better clinical outcomes compared to regional or distant stages (5 yr overall survival 60.8%, 57.9%, and 32.8%; p < 0.0001). In addition, younger (<50) patients showed better overall survival compareed to older (≥50) patients (5 yr overall survival 52.6% vs. 40.2%; p < 0.0001). Conclusions: The incidence of ovarian carcinosarcoma is quite low, with an ASR of 0.064/100,000 during the last 20 years. Ovarian carcinosarcoma had worse clinical outcomes compared to epithelial ovarian cancer.