Intersectoral collaboration has become an essential dimension of public health practice and policy since the mid-1970s. This article reviews the origins, theories, alternate views, and evidence, as well as guidance and training documents pertinent to this field. Although there were some antecedents of intersectoral thinking in the 1970s—for example, World Health Organization, National Environmental Health Programmes: Their Planning, Organization, and Administration; Report of a WHO Expert Committee (Meeting Held in Geneva from 3 to 11 June 1969), World Health Organization Technical Report 439 (Geneva, Switzerland: World Health Organization, 1970)—the heyday of conceptual and rhetorical development fell in the 1980s. The World Health Organization convened expert meetings—for example, Morris Schaefer, Intersectoral Cooperation and Health in Environmental Management: An Examination of National Experience (Geneva, Switzerland: World Health Organization, 1981)—and issued authoritative inventories of the success of intersectoral action—for example, World Health Organization, Intersectoral Action for Health: The Role of Intersectoral Cooperation in National Strategies for Health for All (Geneva, Switzerland: World Health Organization, 1986). This experience, and subsequent calls for further action and policymaking, culminated in a standard of setting conferences where key principles and dimensions of intersectoral action were affirmed; for example, W. Kreisel and Y. von Schirnding, “Intersectoral Action for Health: A Cornerstone for Health for All in the 21st Century,” World Health Statistics Quarterly / Rapport trimestriel de statistiques sanitaires mondiales 51.1 (1998): 75–78. Here, we combine insights from public health, political science, sociology, and public administration to comprehensively map the current body of knowledge.