Background: Breast cancer is a serious public health problem and is the second most prevalent cancer type in the world. The purpose of this article is to evaluate the association between pesticide use and breast cancer in a region of intense agribusiness activity in the state of Mato Grosso, Brazil. Methods: A case-control study was conducted on women living in the city of Rondonópolis, in the south of Mato Grosso state. There were 85 cases of women with confirmed breast cancer and 266 controls who were randomly selected from primary health care users. Bivariate and stratified analyses were performed. Multiple logistic regression was then performed, keeping in the final model the factors with a significance level lower than or equal to 0.05 or considered important according to apriori biological criteria. Results: In the final model, living near cropland with pesticides (OR: 2.37; CI: 95% 1.78-3.16) and women aged over 50 years who experienced early menarche (OR: 2.08; CI: 95% 1.06-4.12) had a higher risk of developing breast cancer compared to control subjects. Conclusion: This study highlights the importance of exposure to pesticides as an environmental risk factor for the development of breast cancer among women.