This study was conducted to investigate the expression of the spindle assembly checkpoint kinase tyrosine/threonine kinase (TTK) in triple positive breast cancer (TPBC) and its effect on TPBC cells. We analyzed the status of TTK in 69 TPBC samples using immunohistochemistry. The correlation between TTK and clinicopathological parameters was analyzed using a chi-squared test. The prognostic value of TTK was evaluated using Kaplan-Meier survival curves. We analyzed the role of TTK in the invasion and proliferation of TPBC cells in vitro and in vivo. The mean age of the 69 patients with TPBC enrolled in this study was 53 years (range: 29-86 years). TTK expression was positively correlated with tumor size (p=0.034), p53 status (p=0.023), TNM stage ([p=0.023), and Ki-67 index (p<0.001). The Kaplan-Meier curves revealed that TTK expression was correlated with poor disease-free survival (p=0.001) and overall survival (p=0.050). Multivariate proportional hazard regression analyses showed that TTK and TNM staging were significant independent predictors of disease-free survival (p=0.007 and p=0.034, respectively). Additionally, TTK knockdown inhibited the invasion and proliferation of the BT474 TPBC cell line. The findings of this study indicate that TTK overexpression is associated with cancer progression and prognosis in patients with TPBC, whereas TTK knockdown inhibits the invasion and proliferation of TPBC cells. Thus, TTK might serve as a prognostic marker for TPBC.