Yes-associated protein (YAP) protein acts as tumorigenic factor in many solid tumors, but the situation in breast cancer is under debate. Here, we would analyze its status in breast cancer. YAP expression in the 110 primary breast cancer and their paired local recurrent tumors was investigated. Clinicopathologic data for age, histologic grading, hormone status, lymph nodes and HER2 status were also gathered and analyzed. 46.4% (51/110) primary breast cancer tissues were positive for total YAP expression which was significantly higher than that in the recurrent tissues (10.9%; P < 0.05). The expression of total YAP protein in the primary breast cancer tissues was positively associated with the tumor size, especially in triple negative breast cancer (TNBC) subtype (P < 0.05). Higher total or nuclear YAP expression in the primary tumor was correlated with poor disease-free survival among patients with TNBC (P < 0.05). In the multivariate models, nuclear YAP expression was an independently prognostic factor in TNBC. High total or nuclear YAP expression predicts poor prognosis among patients with TNBC. It might be a therapeutic target for TNBC in the future.