Agricultural marketing cooperatives are of panoramic socioeconomic importance. As owners, decision-makers, and suppliers, their members' opportunism is of great concern to their competitiveness. In this study, we analyze sthe impact of governance mechanisms on opportunism. We explore the nonlinear effects and differences between the memberships of first-tier cooperatives and federated cooperatives. Empirical results show that not all the mechanisms are equally effective: effective mechanisms for first-tier cooperatives memberships should be employed with lower intensity, whereas those effective for federated cooperatives memberships need a higher intensity of employment. The results of this study allow presenting theoretical and managerial implications in an underexplored field of research.