ABSTRACT:Introduction: breast cancer is one of the main causes of death among women in Brazil and worldwide. The diagnosis of breast neoplasms usually represents an emotional burden, and it may lead to adjustment reactions and even be the trigger for affective disorders (mainly depression), anxiety or psychosis. The Beck Depression Inventory (BDI) is one of the most used mechanisms for the evaluation of depression in research and in clinics. Depression prevalence in patients with cancer varies from 3% to 55% among different studies. Methodological variation, different instruments to assess depression and different cut-off points for diagnosis contribute to the huge discrepancy in current findings. In general, the more specifically depression is defined and evaluated, the lower the rates of prevalence are reported. Many articles fail to demonstrate a statistical significance in the relationship between depression and cancer-specific factors. This suggests that risk factors for depression in those patients are more related to the patient as contextual variables and premorbid factors of personality -and not to the cancer or its treatment. Objective: to determine the prevalence of major depression in women with breast cancer. Methods: a cross-sectional study was conducted in women with breast cancer. The sample consisted of 51 patients who answered the Beck Depression Inventory (BDI). The presence of depression was considered in cases where the scores were above 20. A questionnaire with additional data about the patients such as age, marital status, ethnicity, education, family income, family history of depression and breast cancer, and cancer-related variables including staging, months since diagnosis, treatment modality, type of surgery, alopecia occurring were used. Descriptive analysis and test of association (chi-square) were conducted. Results: the prevalence of major depression was 5.9%, similar to that observed in community samples. Subsyndromal depressive symptoms had a score of 21.6% (BDI scores from 16 to 20). Chi-square test was conducted and showed no statistically significant relationship between the classification of BDI and the variables tested (characteristics related to patient and cancer-specific). This indicates that the isolated context of the variables does not influence the event of depression. Conclusion: the prevalence of major depression in women with breast neoplasms was 5.9%.