Abstract: Breast cancer, one of the most common malignant tumors in women, continues to rise in incidence worldwide and remains a leading cause of cancer-related morbidity and mortality among women, posing a serious threat to female health. Tumor-associated eosinophils, as key immune effector and regulatory cells within the tumor microenvironment, play multifaceted roles in the initiation, progression, and metastasis of breast cancer. They can directly impact tumor cells as well as modulate immune responses and reshape the tumor microenvironment, thereby influencing treatment outcomes. With advances in immunotherapy, the critical role of eosinophils in mediating responses to breast cancer immunotherapy has become increasingly evident. This article elucidates the functions of eosinophils in breast cancer progression and discusses their potential value in early diagnosis, prognostic assessment, and targeted therapy, in light of current treatment strategies. The aim is to provide new perspectives and directions for comprehensive breast cancer management.