Epidemiological studies have found obesity to be a risk factor for women's breast cancer. The present study was to investigate whether there is a relationship between serum levels of leptin, insulin, and lipids and breast cancer incidence, in order to find experimental evidence that would be helpful in the diagnosis and prevention of breast cancer. Blood samples were collected from 130 patients with mammary disease and 103 healthy control subjects. Serum leptin, insulin, and lipids were determined by radioimmunoassay (RIA), enzyme-linked immunosorbent assays (ELISA), and Biochemistry Auto-analyzer, respectively. The data analysis was performed by use of the SPSS10.0 computer software. We found that the serum levels of leptin, insulin, and triglyceride (TG) were clearly higher in patients with breast cancer than in patients with benign breast disease and healthy controls, while serum HDL-C levels were lower in breast cancer patients (p < 0.03). Moreover, serum leptin levels were significantly correlated with BMI (body mass index) among three groups, whereas serum insulin levels were unrelated to BMI among three groups. Furthermore, the serum levels of leptin and insulin were not associated with menopausal status in patients with mammary disease (p > 0.05); however, the serum levels of F-Chol, T-Chol, TG, LDL-C, and APOB were significant higher in postmenopausal cases than those in premenopausal cases (p < 0.025). Interestingly, logistic regression analysis showed that subjects with elevated serum levels of leptin, insulin, TG, APOA1, and reduced level of serum HDL-C displayed increased risk of developing breast cancer than those with the normal levels, respectively. In conclusion, the present study suggested that aberrant serum levels of leptin, insulin, and lipids might play an important role in carcinogenesis of breast cancer. The elevated serum levels of leptin, insulin, TG, APOA1, and reduced level of serum HDL-C may be correlated with increased risk of breast cancer, suggesting that one way of preventing breast cancer would be carried out by controlling the intake of food.