The theory of practicing values may provide valuable insight into the role of organizational values in sport organizations. This is particularly relevant in the nonprofit sport sector where managers operate with limited budgets and organizations may subscribe to specific ethical-social values related to organizational performance. The purpose of this study was to explore the influence of organizational values on the performance of nonprofit sport organizations and the possible mediating effect of employing a management-by-values approach. Online questionnaires were collected from 24 national sport organizations, with a total sample of 103 participants. Results indicate management by values fully mediates the influence of ethical-social organizational values on organizational performance. These results are explained using the theory of practicing values, which emphasizes the need to intentionally manage values within sport organizations. Implications for research and practice are presented.