Health care organizations are facing rapid changes, frequently involving modification of existing procedures. The case study reported here examined change processes and learning in a health care organization. The organizational change in question occurred in the emergency clinic of a Finnish central hospital where a new action model for shift-specific nursing supervision was being introduced. The aim of this study was to investigate some of the employee participation and learning opportunities amid this organizational change. The data collection was ethnographically informed, and the data consisted of audio-recorded and observed meetings, observations of the new action model, and field interviews which were analyzed qualitatively. The change appeared to occur in four phases: preparation, planning, discussion, and implementation. Structures (e.g. regular meetings open to the entire staff) and practices (e.g. open discussion) facilitating participation in the phases of the change were prerequisites for participation by individual employees, but participation was not made structurally possible throughout the change. The study confirmed the importance of participation for learning within change. In the change, participation in the form of identity work denoted individual-level learning opportunities, and participation in the form of suggestions for new practices and expression of problems facilitated organization-level learning opportunities. In this study, participation manifested itself as a more multifaceted phenomenon than in previous studies. This study provided new knowledge on employee participation and its manifestations in micro-level interaction, as well as on both individual-level and organization-level learning opportunities in organizational change.