Background: Triple-negative breast cancer (TNBC) is a subtype of breast cancer characterized by the lack of estrogen, progesterone, or human epidermal growth factor 2 (HER2) receptor expression. TNBC has poor prognosis due to its high metastatic potential and limited treatment options. Shugoshin-1 (Sgo1), a centromeric protein that maintains stability in chromatids during mitosis, has been thought to play an important role in the progression of TNBC. Previous publications from our group have shown that the transient downregulation of Sgo1 in TNBC cells decrease the epithelial-to-mesenchymal transition (EMT), which is a precursor of metastasis. Our purpose with this study is to evaluate the role of long-term effects of Sgo1 downregulation in cell invasion, cell migration, tumor growth, and metastasis. Methods: To achieve our goal, MDA-MB-231 cells were stably transfected with a lentivirus containing a shRNA Sgo1 sequence or a scramble shRNA control. Cell invasion and migration were evaluated by Boyden chamber assays. Meanwhile, tumor growth and metastasis were evaluated using an immunocompromised orthotopic mice model. Female NOD-SCID Gamma (NSG) mice were injected either with 2.5 X 10⁶ shRNA Control (n= 10) or shRNA Sgo1 (n= 10) MDA-MB-231 cells. Tumor growth was measured for eight weeks using a vernier caliper. Afterwards, primary, and metastatic tumors as well as primary organs were harvested. Lung and liver samples were embedded in paraffin and stained with hematoxylin and eosin. A Student t test was used to evaluate the differences between groups. A p-value < 0.05 was considered significant. Results: Our results show a significant reduction in cell invasion and migration in MDA-MB-231 cells treated with shRNA Sgo1. Moreover, we observed a significant reduction in tumor growth and metastasis to lymph nodes, liver, and lungs in the mice treated with shRNA Sgo1 when compared to shRNA Control group. Conclusions: These results suggest that Sgo1 is an important regulator in TNBC tumor growth and metastasis through the modulation of EMT genes. Thus, targeting Sgo1 early in the course of TNBC can be a potential therapeutic treatment of TNBC.