OBJECTIVE To explore the expression of Tau protein in breast invasive ductal carcinomas and examine the correlation between its expression and clinicopathological characteristics of breast cancer. METHODS The clinicopathological data of 150 breast cancer patients at Third Municipal Hospital from October 2007 to June 2011 were collected and analyzed. Immunohistochemical method was used to detect the expressions of estrogen receptor (ER), progesterone receptor (PR), HER-2 and Tau protein. RESULTS No correlations existed between the expression of Tau protein and age, tumor size or node metastasis of breast cancer patients (χ(2) = 0.02, P = 0.88; χ(2) = 0.55, P = 0.46; χ(2) = 1.02, P = 0.31). The expressions of Tau in ER positive patients were significantly higher than ER negative patients. And this trend extended to PR positive and HER-2 negative patients (χ(2) = 15.77, P = 0.00; χ(2) = 5.03, P = 0.03; χ(2) = 8.00, P = 0.01). The expression of Tau protein in Luminal A subtype was significantly higher than in Luminal B subtype, HER-2 over-expression subtype and basal like subtype (χ(2) = 7.26, P = 0.01). CONCLUSIONS Over-expressed in breast cancer, Tau protein is associated with ER, PR and HER-2. However, the relation between Tau protein and prognosis of breast cancer requires further researches.