With the increase in the number of new cases of breast cancer worldwide, increasing attention has been given to research related to its incidence and treatment. As an endocrine hormone, prolactin (PRL) is mainly secreted by the anterior pituitary gland, and its production is affected by many factors, such as human behavior, diet, and environment. It can also bind to prolactin receptors (PRLRs) through autocrine/paracrine effects in breast cells, activate downstream signal transduction pathways, and play an important role in the occurrence and development of breast cancer. However, according to the results of current epidemiological studies, in vivo and in vitro experiments, genetic analysis, and other research results, there are still relatively contradictory results regarding the role of PRL in breast cancer. On the one hand, PRL can increase the incidence of breast cancer; promote tumor cell proliferation and survival; and regulate angiogenesis, movement, invasion, and metastasis. On the other hand, PRL plays a role in maintaining tissue differentiation and inhibiting the process of breast cancer epithelial-mesenchymal transition (EMT). In addition, in the era of precision medicine, the mechanism of action and efficacy of new targeted therapy drugs targeting PRLR are constantly being explored. Therefore, this article focuses on the research progress of the role of PRL and its receptors in breast cancer.