More imaging centers are incorporating diffusion-weighted imaging (DWI) into the clinical breast magnetic resonance (MR) examination, with the potential of increasing the specificity of breast MR imaging. This article reviews the role of DWI in the evaluation of breast lesions. The principles, technique, and protocol of DWI are discussed, including the importance of the chosen b value. The interpretation strategy, including quantitative and qualitative analysis is described. Clinical applications of breast DWI are evaluated, such as distinguishing malignant from benign lesions, tumor characterization and monitoring treatment planning, and potential pitfalls such as false-negative and false-positive findings are discussed.