Purpose: This article explores how voluntary certifications influence the way cooperatives provide advisory services to their members and the influence of these services on agricultural practices. Design/Methodology/Approach: Case studies were conducted in four representative Costa Rican cooperatives interviewing twenty interviewed cooperative administrators and members to determine changes in advisory services and farming practices over the past twenty years and factors which influenced those changes. Findings: Certifications induce cooperatives to offer new services to support farmers. Cooperatives form collaborations with new stakeholders or reconfigure existing collaborations to provide advisory services to their members. These services have helped to shape farmers' attitudes about sustainable farming practices, though farm-level changes may be small. The main change at the cooperative level is adding new topics for group training, and certification issues are directly linked with practices such as maintaining a farm record book or wearing a mask when applying pesticides. Practices which compete with productivity are unlikely to change. Practical Implications: The results are useful to improve the advisory services provided by cooperatives by better identifying the key issues to be addressed to fulfill the certifications' requirements. Theoretical implications: Cooperatives are a relevant player to induce more sustainable practices, by providing or coordinating advisory services, but their efforts cannot be seen disconnected from a broader institutional environment. Originality/Value: We demonstrate that certifications change the intensity and scope of advisory services and induce cooperatives to engage with a more diverse network of stakeholders.