This study explores the governance intricacies in establishing a large-scale information infrastructure for integrated care within the National Health Service of England. By focusing on the initial 5years of a regional interoperability program, we examine the challenges and dynamics of creating a unified system across organizational boundaries. A longitudinal multi-methods approach was utilized, collecting data through interviews with health and social care personnel involved in project governance, meeting observations, and document analysis. This provided an in-depth understanding of the processes and challenges of developing the regional interoperability program. This study reveals a dynamic negotiation process and evolving governance structures that must continuously adapt to integrate diverse systems. Key findings include challenges in reconciling multiplicity and heterogeneity, the importance of social learning and stakeholder adaptation, and the role of ongoing negotiation and collaborative group construction in implementing interorganizational infrastructures. This study underscores the necessity of continuous adaptation and negotiation among stakeholders in establishing effective governance of integrated care infrastructures. Social learning and active participation play pivotal roles in overcoming the challenges associated with system integration. Strategic insights from this research can guide stakeholders in developing sociotechnical solutions for digital interorganizational infrastructures in integrated care.