Breast cancer is a malignancy which is characterized with high invasion, metastasis, and recurrence rate. The tumor microenvironment is a key player which supports the development and progression of cancerous cells. Alongside fibroblasts, epithelial cells, stromal cells, immune cells, extracellular vesicles, and soluble factors, adipocytes are the largest components of breast tissue. Breast cancer’s invasive front contains the abnormal adipocytes, also known as cancer-associated adipocytes (CAAs). When compared to mature adipocytes, CAAs exhibit a distinct phenotype and interact differently with breast cancer cells. Multiple adipokines (adiponectin, leptin, chemokines, and cytokines) that play significant roles in different biological processes, including cellular proliferation, invasion, angiogenesis, dissemination, and metastasis of breast cancer cells, are secreted in the extracellular environment by CAAs. We emphasized the role of CAAs in the development of breast cancer in this chapter, along with metabolic reprogramming, immune cell adjustment, adipokine modulation, and extracellular vesicle-mediated signaling. By deciphering interaction CAAs mechanisms in the tumour microinveroment, will provide important information for unveiling breast cancer oncogenesis and progress, and novel strategies to design therapeutic approaches targeting breast cancer cells.