Among various types of cancers, breast cancer is one of the most frequent and major reasons of cancer death among women worldwide. It has the ability to spread to different organs of the body and develop metastases. Till date, chemotherapy is the most common option for the treatment of breast cancer. However, chemotherapy is not a very successful strategy to cure breast cancer and has decreased the survival rates according to the different breast cancer reports. The inability to deliver a specific drug to the target tissue/cell that causes toxicity to the normal healthy tissue/cell is the primary concern in the chemotherapy. Most of the chemotherapeutic drugs used in conventional chemotherapy have low aqueous solubility and high pre-systemic metabolism; therefore, they are biologically less available to the target location and affect normal healthy tissues/cell as well. Since the last decades, the development of nanoparticle technology has opened a new option in the successful treatment of breast cancer due to the various unique advantages offered by this nanoplatform. Among them, polymeric nanomedicines become the promising choice as the effective drug delivery system and provide great potential in the management of breast cancers as per the outcome of different preclinical studies. Polymeric nanomedicines may exhibit their anticancer efficacy either via passive or active targeting approach. Polymeric nanomedicines can be actively targeted by its surface conjugation to the breast cancerspecific targeting ligands. Active targeting of the nanomedicines has the ability to deliver the specific drug to the target site, therefore, healthy cells remain unaffected by active targeting. Moreover, polymeric nanomedicines have also been exploited in breast cancer treatment through gene therapy. This chapter summarizes the extensive literature of preclinical findings on polymeric nanomedicines exploited in the treatment of breast cancer.