Knowledge integration is the raison d’etre for the existence of the firm (Grant, 1996a; Kogut & Zander, 1992) and has been widely studied across many subfields in management and organizational studies. However, few constructs have received as much scholarly attention as knowledge integration while remaining so equivocally defined and measured, leading to a confusing array of conceptualizations, undermining its theoretical, empirical, and practical usefulness. As a theoretical construct, knowledge integration also cuts across the macro-and microlevels, gaining attention from scholars interested in explaining the microfoundations of strategy and capabilities (e.g., Felin & Hesterly, 2007; Lewin, Massini, & Peeters, 2011). However, the interplay among these micro and macro factors is often overlooked, and its implications for theory building are ignored. To address these issues, we examine and integrate micro-and macro-organizational perspectives on knowledge integration. We provide a review of its definitions and offer our definition based on key dimensions identified. We discuss and analyze the micro and macro perspectives, presenting key assertions, propositions, limitations, and conclusions from representative studies. Finally, we integrate the diverse perspectives we discuss, showing how their interplay can enrich future scholarship and our understanding of knowledge integration as a key organizational construct.