Background: Patient participation in decision-making has become a hallmark of responsive healthcare systems. Cancer programs in many countries have formally committed to involving people living with and beyond cancer (PLC) at multiple levels of network-based services. However, PLC participation in the governance of these networks remains highly variable for reasons that are, as yet, poorly understood. This study explores how PLC participation takes shape within cancer network governance. Methods: This case study, using a qualitative approach in a natural setting, aimed to identify mechanisms that enable PLC participation in governance. It was conducted over six years in four local cancer networks in Québec (Canada), where PLC representation was prescribed by the Cancer Directorate. Data were collected from documents, meeting observations, and interviews with actors (n=89) involved in national and local cancer governance committees: policymakers, managers, clinicians and PLC. These data were triangulated and iteratively analysed according to a framework based on functions of collaborative governance in the network context. Results: Main mechanisms enabling PLC participation are: 1) emphasis on patient-centred care as a network objective; 2) opportunities to shape mandated PLC representation into participation; and 3) recognition of PLC knowledge in decision-making. The shared vision of person-centred care facilitates PLC participation. The quality of participation improves through changes in how committee meetings are conducted, and through the establishment of a national forum in which PLC pool their experience, develop skills and establish a common voice on priority issues. PLC knowledge is especially valued around particular challenges such as designing integrated care trajectories and overcoming barriers to accessing care. These three mechanisms interact to enable PLC participation in governance and are activated to varying extents in each local network context.Conclusions: This study reveals that mandating PLC representation on governance structures is a powerful context element enabling participation, but that it also delineates which governance functions are open to influence from PLC participation. While the activation of mechanisms is context dependent, the insights from this study in Québec are transferable to cancer networks in other jurisdictions seeking to embed PLC participation in decision-making.