Although a substantial literature examines the relationship between culture and health in myriad individual contexts, a lack of comparative data across settings has resulted in disparate and imprecise conceptualizations of the concept for scholars and practitioners alike. This article examines scholars and practitioners' understandings of culture in relation to health interventions. Drawing on 169 interviews with officials from three different nongovernmental organizations working on health issues in multiple countries—Partners in Health, Oxfam America, and Sesame Workshop—we examine how these respondents' interpretations of culture converge or diverge with recent developments in the study of the concept, as well as how these understandings influence health interventions at three different stages—design, implementation, and evaluation—of a project. Based on these analyses, a tripartite definition of culture is built—as knowledge, practice, and change—and these distinct conceptualizations are linked to the success or failure of a project at each stage of an intervention. In so doing, the study provides a descriptive and analytical starting point for scholars interested in understanding the theoretical and empirical relevance of culture for health interventions, and sets forth concrete recommendations for practitioners working to achieve robust improvements in health outcomes.