Given that humans are inherently social beings, it is remarkable that research on mindfulness has focused primarily on individual outcomes such as cognition, performance, and well-being. In this chapter, we discuss the relational impact of mindfulness and show that the scope of mindfulness lies far beyond the individual. We introduce the MIRROR model, which stands for Mindfulness in Relationships, Regulation of Responses model. The model describes how mindfulness affects various intra-individual psychological processes, which, in turn, affect various interpersonal outcomes. Although we draw mainly on theory and research in the realm of romantic relationships, we discuss how the MIRROR model can generate testable predictions about the role of mindfulness in social relationships more broadly. We also discuss gaps in the literature and the practical implications of the MIRROR model for the utility of mindfulness-based couple interventions.