Abstract: Tumor dormancy refers to the status of disseminated cancer cells that remain in a viable yet not proliferating state for a prolonged period. Dormant cells will eventually "re-awake" resume their proliferation, and produce overt metastasis. The dormancy mechanism of cancer has attracted attention because of the close relationship between late recurrence and tumor dormancy. In this review, we illustrate the latest discoveries on the biological underpinnings of breast cancer dormancy and offer clinicians an overview of dormancy in breast cancer to guide them in the basic understanding of the complexity that underlies this process.