Cancer-associated fibroblasts (CAFs) are one of the major stroma cells in tumor microenvironment. CAFs are usually derived from the normal fibroblasts by the actions of various platelet derived growth factor and fibroblast growth factor, interleukin 6 and hepatocyte growth factor, or from the mesenchymal stem cells, fat cells and other cells during the process of epithelial mesenchymal transformation (EMT), and some CAFs are transformed from cancer stem cells. Recent studies have demonstrated that the CAFs in breast cancer can promote the invasion and metastasis of breast cancer cells through secreting a variety of cytokines and exosomes, and participating in EMT and extracellular matrix remodeling, and also promote the growth and invasion of the breast cancer cells under the hypoxic tumor microenvironment through activating the relevant signaling pathways. Moreover, CAFs mediate the chemotherapy resistance, endocrine therapy resistance and multi-drug resistance in breast cancer through various ways such as elevating the apoptosis threshold, serving as a physical barrier against anti-tumor drugs, secreting glutamine for increasing the survival rate of breast cancer cells, activating the growth factor-associated signaling pathways or increasing mitochondrial function to produce anti-apoptotic effects. Here, the authors mainly address the research progress in sources of CAFs and its role in invasion/metastasis and treatment resistance of breast cancer.