Byline: Heesun Chae, Jisung Park,Jin Nam Choi Keywords: achievement striving; conscientiousness; coworker support; dutifulness; knowledge-sharing behavior; situation strength; social dilemma; supervisor support; trait activation Summary This study adopts self- and other-centered approaches to explain how the two facets of conscientiousness (i.e., dutifulness and achievement striving) distinctly resolve knowledge sharing dilemmas among employees. It also explores how the critical social surroundings of employees (i.e., supervisor support and coworker support) neutralize or activate the effects of dutifulness and achievement striving on knowledge-sharing behavior. Our analysis of the data collected from 150 employee-supervisor dyads corroborates that the other-centered facet of conscientiousness (dutifulness) is positively related to knowledge-sharing behavior, whereas the self-centered facet (achievement striving) is negatively related to the same behavior. The analysis also affirms that the positive effect of dutifulness and the negative effect of achievement striving on knowledge sharing are strengthened when supervisor support is low and coworker support is high. This study offers theoretical and practical implications relevant to knowledge management in organizations, distinct roles of facet-specific personalities toward knowledge sharing, and contrasting personality-situation interactions by situation strength and trait activation in shaping employee behavior. Biographical information: Heesun Chae earned her doctoral degree in Organizational Behavior and Human Resource Management at Seoul National University. Her research interests include task design, creativity, and group processes. Jisung Park is Assistant Professor of Organizational Behavior at Chungnam University. She earned her doctoral degree in Human Resource Management at Seoul National University. Her research interests include strategic human resource management, diversity, and knowledge sharing in organizations. Jin Nam Choi (email@example.com) is Professor of Management at Seoul National University, South Korea. He earned his Ph.D. in Organizational Psychology from the University of Michigan. His research interests include innovation implementation, organizational creativity, and multilevel processes of human behavior in organizations.