Breast cancer is the second leading cause of cancer deaths and is the most common cancer among women. Although a number of biomarkers are being used in clinical practice, significant number cases for breast cancers are detected late and difficult to treat. Therefore, new biomarkers are in need to improve diagnosis and the therapeutics for breast cancer. The emergence of proteomics technologies has facilitated researcher comprehensive differential expression analyses of proteins in healthy and cancer individuals. The most commonly used proteomic techniques in breast cancer research are 2D-PAGE, SELDI-ToF MS, Protein Arrays, ICAT, iTRAQ and SILAC. Recent advancement in proteomics has also enabled to study the intracellular signalling pathways that may underlie the development of breast cancer. Thus, proteomics could play significant roles in identification of novel biomarkers and/or drug targets to improve existing prognosis and diagnosis of breast cancer. This book covers a selection of advances in the realm of proteomics and its promise for the discovery of biomarkers and drug targets, and sample preparation of cell culture and clinical martial for breast cancer research.