Background: Approximately 15% of breast cancers lack expression of Estrogen Receptor (ER), Progesterone Receptor (PR) and Human Epidermal Growth Factor Receptor 2 (HER-2), and are referred to as Triple Negative Breast Cancer (TNBC). Clinical outcomes in patients with TNBC continue to be poor due to inherently aggressive biology of the disease and paucity of targeted therapies. In this study, we identified Cell Division Cycle protein 20 (CDC20), a key regulatory protein that mediates sister chromatid separation in mitosis, as a novel therapeutic target in TNBC. Methods: To uncover new drivers of TNBC, we nominated genes that are significantly overexpressed in patients with TNBC, compared to non-TNBCs. After identifying CDC20 as a top hit in this analysis, we used expression microarrays, RNA-seq analyses and Western blotting to assess CDC20 expression levels in breast cancer patients and cell lines. Kaplan-Meier analyses were performed to study the correlation between CDC20 expression levels and clinical outcomes, including recurrence-free survival, metastasis-free survival and overall survival. shRNA-mediated knockdown of CDC20 in TNBC cell lines was employed to study the role of CDC20 in TNBC proliferation, invasion, migration and xenograft growth in mice. Results: CDC20 was significantly overexpressed in TNBCs (compared to non-TNBCs) in The Cancer Genome Atlas (TCGA) breast dataset, and in several other independent breast cancer datasets, including Curtis, Stickeler and Kao. CDC20 expression was also significantly higher in TNBC cell lines compared to non-TNBC cell lines. Furthermore, expression levels of CDC20 were highly significantly correlated with clinical outcomes, including recurrence-free survival, metastasis-free survival and overall survival. shRNA-mediated knockdown of CDC20 expression in TNBC cell lines, MDA-MB-231 and MDA-MB-468, resulted in decreased proliferation, invasion and migration. Our preliminary findings suggest that CDC20 knockdown also results in inhibition of cell line-derived xenograft growth in mice. Conclusion: We identified CDC20 is a novel therapeutic target in TNBC. Our findings support development of pharmacologic strategies to inhibit CDC20 function as a potential targeted therapy against TNBC. Citation Format: Sharma J, Raicu I, Nguyen J, Udden N, Wang Q, Alluri P. CDC20 is a novel therapeutic target in triple negative breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P2-06-20.