Knowledge transfer within organizations has important implications for organizational performance and competitive advantage. In this virtual special issue, we review articles on this topic published in Organization Science between 2014 and 2020 and identify 53 articles for their theoretical and empirical contributions. These articles examine knowledge transfer through five transfer mechanisms: social networks, routines, personnel mobility, organizational design, and search. We consider the intersection of each transfer mechanism with important components of knowledge transfer (characteristics of sources/recipients, characteristics of knowledge, and characteristics of contexts). We present 15 exemplar articles, each of which reflects the intersection of a mechanism and a component of knowledge transfer. We also present an overview of the methodological approaches and empirical contexts that are utilized. We conclude our article with a discussion of future research opportunities. The articles published in Organization Science have advanced understanding of both the mechanisms through which knowledge transfer occurs and the conditions under which it is most likely.