Abstract: Endocrine therapy is the mainstay for patients with hormone-receptor-positive metastatic breast cancer because of its efficacy and safety. With the development of new and efficacious agents, including cyclin-dependent kinase (CDK) 4/6 inhibitors, the options for endocrine therapy have expanded. CDK4/6 inhibitors combined with endocrine therapy have been shown to improve survival and delay the time to chemotherapy in patients with hormone-receptor-positive metastatic breast cancer. Accordingly, the treatment strategies for hormone-receptor-positive metastatic breast cancer are changing around the world. This review aims to summarize and discuss the progress of therapy with CDK4/6 inhibitors in patients with hormone-receptor-positive metastatic breast cancer.