Objective: To investigate the relations of the levels of endogenous sex hormones and blood lipids with breast cancer in postmenopausal women and the feasibility of using them as predictors for breast cancer. Methods: Two-hundred and seventy-four postmenopausal women with breast cancer (breast cancer group) undergoing surgical treatment from July 2011 to June 2014, and 279 postmenopausal female patients admitted during the same period for other diseases who were excluded from breast diseases (control group) were enrolled. The levels of sex hormone and blood lipids between the two groups were compared, and the potential predictors for breast cancer were analyzed. Results: The levels of estrogens (E2) and testosterone (T) in breast cancer group were significantly higher than those in control group (both P<0.05), while levels of other sex hormones and blood lipids showed no significant difference between the two groups (all P>0.05). Stratification analysis demonstrated that the incidence of breast cancer was increased with either E2 level or T level, in which E2 level had a better sensitivity and specificity for prediction of breast cancer, and its area under curve (AUC) of the receiver operating characteristic (ROC) reached 0.730 (95% CI=0.649–0.811), but T level showed no significance in prediction of breast cancer. Conclusion: The E2 and T levels are associated with breast cancer in postmenopausal women, and E2 level can be used as one of the predictors of breast cancer, but has not yet become a satisfactory or excellent standard.