Background <p>Patient and public involvement (PPI) is increasingly integrated into healthcare and health research, yet its role in driving culture change remains poorly understood. Culture change is a complex and multifaceted concept, and it is difficult to define and evaluate. This study set out to identify culture-related outcomes of PPI across clinical, organizational, and research domains, and to develop a framework for conceptualizing culture change as an impact of strategic PPI efforts.</p> Results <p>Twenty-two studies met the inclusion criteria, yielding 132 outcomes linked to culture change. These outcomes were thematically synthesized into 15 categories and 5 subcategories and situated within a three-level structure: micro (user socialization process), meso (organizational commitment), and macro (regulatory assumptions). Using abductive thematic analysis, we developed theory across the empirical findings to develop the PPI Culture Change (PPI-CC) model – the first multi-level, empirically grounded, and theory-informed framework to conceptualize how PPI contributes to culture change in healthcare and health research.</p> Conclusion <p>The PPI-CC model positions culture change as an impact of PPI in its own right. Drawing on multi-cultural and complexity-informed perspectives, it conceptualizes culture change in the context of PPI in healthcare and health research as a multidimensional, iterative, and dynamic process shaped by interaction, feedback, learning, and adaptation across micro, meso, and macro levels. The model should be viewed as a conceptual starting point rather than a practice-ready tool, and it proposes that evaluation of culture change be approached as a process of learning.</p>