Background: In the development of breast cancer (BC), estrogen exposure and the increase in breast density (BD) are two determinant factors for BC risk. Objective: To identify the relationship between the XbaI and PvuII polymorphisms in the estrogen receptor (ER-alpha) with BD. Material and methods: Cross-sectional study which included 225 women, aged 40-65 years, without evident cancer data, who underwent routine mammography for early BC diagnosis in a radiology department. Two groups were formed: women with increased and with normal BD. Participants were genotyped for the XbaI and PvuII polymorphisms. Results: 19.1% had normal weight, 37.7% overweight, and 43.2% were obese women. In relation to high-risk patterns, 105 women had increased BD and 120 had normal BD (53.3%). The frequency of women with increased BD was also lower in postmenopausal women. Regarding the type of BD, there was no statistically significant difference between frequencies of PvuII and XbaI genotypes. Logistic regression showed that only age and body mass index (BMI) were associated with BD. Conclusion: PvuII and XbaI ER-alpha genotypes were similar among women with dense and non-dense breasts; differently, other factors were associated with BD (age, BMI and menopausal status). Therefore, emphasis should be placed on clinical practice in the relationship between BMI and BD