Introduction: Depression is frequently associated with breast cancer. Although its prevalence and its impact on patientsquality of life are far from negligible, depression is often under-diagnosed and less treated. Objectives: Our study aims to estimate the prevalence of depression in breast cancer patients, to describe their socio-demographic and clinical profile, and to determine the factors associated with this depression. Material and Methods: We carried out a cross-sectional, descriptive and analytical study, conducted from October to December 2021 at the Mohammed IV Cancer Treatment Center. The survey included 100 breast cancer patients. It was conducted using an anonymous questionnaire and the Beck scale to diagnose depression and to assess its severity. Results: Depression in a major form was diagnosed in 52% of breast cancer patients. Age under 40, psychiatric antecedents, metastatic breast cancer, refusal of treatment, heavy treatment regimens and the alteration of the conjugal relationshipwere the factors most associated with higher prevalence of depression in these patients. In the light of what has been demonstrated in the analytical study, we note that the occurrence of a major depressive episode is significantly correlated with the following parameters - Age ranging between 20 and 40 years. - Metastatic spread of breast cancer. - Negative attitude of the spouse. - Relapse of the cancerous disease. Discussion and Conclusion: The high prevalence of depression in breast cancer patients as well as the influence of personal characteristics and treatment in the occurrence of this ailment have been confirmed by several authors. We propose some suggestions to improve the psycho-oncological care of patients with breast cancer, in order to prevent the occurrence of depression in this population.