Breast cancer is the most common cancer and the leading cause of cancer death in women worldwide. Although huge progress has been made in managing early-stage breast cancer, no effective strategy can prevent or treat breast cancer metastasis which has high recurrence rate and high mortality rate. Thus, identification of new molecular markers for the diagnosis and prognostic prediction of metastatic breast cancer and development of innovative therapeutic measures are urgently needed. Recently, epigenetic regulation of the expression and function of oncogenes by aberrant N⁶-methyladenosine (m⁶A) modification of mRNA in aggressive breast cancer is investigated widely. In this review, we retrieve and analyze the most recent studies on m⁶A modification, and summarize the expression and the function of m⁶A regulatory proteins, including the writers, erasers and readers, in the tumorigenesis and progression of breast cancer, and point out the defects in the recent field of m⁶A-related researches, so as to provide scientific basis for diagnosis, therapies and prognosis in breast cancer.