Despite the importance of communication for relationship functioning and maintenance, even partners who love each other often struggle to communicate effectively. Although conflict is inevitable in close relationships, couples vary significantly in their capacity to resolve disagreements. Partners also often struggle to communicate support and comfort to one another in sensitive ways during stressful times. The purpose of this dissertation was to examine the role of neural synchrony in empathy-associated brain regions on couples’ communication throughout social support and conflict interactions. Towards this end, the primary aim of Study 1 was to examine associations between neural synchrony in regions corresponding with perspective taking and post-conflict outcomes in couples. Expanding on Study 1, the primary purpose of Study 2 was to examine and compare effects of neural synchrony corresponding to two different forms of empathy (perspective-taking and empathic distress) on post-support outcomes in couples. Expanding on Studies 1 and 2, the primary aim of Study 3 was to capture and assess time- dependent dynamics between neural synchrony and observed behavior throughout couples’ conflict and social support interactions as they unfold. In line with this aim, I assessed concurrent associations between second-to-second neural synchrony and second-to-second observed behavior, as well as bidirectional lagged associations between neural synchrony and observed behavior across various time-intervals. Findings from the dissertation overall shed light on the complicated nature of empathy and how it may impact communication and close relationships, in which separate facets of empathy relate to communication in different ways and behave differently across various social contexts. Only thinking of empathy as a stable, trait-based construct is likely an oversimplification, as this research shows that it’s the dynamic shifts throughout communication in real time that correspond to changes in behavior. To further our knowledge regarding associations between neural synchrony in empathy-related regions and relationship functioning, future research may consider examining these associations across diverse couples using a mixed methods approach with both cross-sectional and longitudinal methods.