The paper explores and ranks the key factors that support tacit knowledge sharing in automotive assembly lines. Existing studies on knowledge sharing tend to overwhelmingly focus on knowledge-intensive, white-collar work, and despite the acknowledgment of the importance of blue-collar workers' tacit knowledge, both the knowledge management and operations management literature have devoted limited attention to manufacturing environments, and, in particular, those working on assembly lines. This study draws on qualitative and quantitative data from workers and plant managers of an automotive assembly line located in the Brazilian automotive Modular Consortium (MC), a unique production concept which produces vehicles in high volume and high variety. MC works with six multinational suppliers, which interact directly on the assembly line, sharing physical space, responsibilities, and quality control. The qualitative element of the study included interviews, informal conversations, and on-site observations. Transcriptions were interpreted using content analysis. The quantitative element entailed a comparison of worker and management survey responses on the relative importance they ascribe to the different factors contributing to knowledge sharing, by ranking them using Analytic Hierarchy Process (AHP). The findings compare and contrast the perspectives of managers and workers on knowledge sharing with reference to factors related to people and processes. Implications for managerial action based on knowledge, HRM, and work management are discussed.