Interpersonal synchronization of inferior frontal cortices tracks social interactive learning of a song

&NA; Much of human learning emerges as a result of interaction with others. Yet, this interpersonal process has been poorly characterized from a neurophysiological perspective. This study investigated (i) whether Interpersonal Brain Synchronization (IBS) can reliably mark social interactive learning, and specifically (ii) during what kind of interactive behavior. We recorded brain activity from learner‐instructor dyads using functional Near‐Infrared Spectroscopy (fNIRS) during the acquisition of a music song. We made four fundamental observations. First, during the interactive learning task, brain activity recorded from the bilateral Inferior Frontal Cortex (IFC) synchronized across the learner and the instructor. Second, such IBS was observed in particular when the learner was observing the instructor's vocal behavior and when the learning experience entailed a turn‐taking and more active mode of interaction. Third, this specific enhancement of IBS predicted learner's behavioral performance. Fourth, Granger causality analyses further disclosed that the signal recorded from the instructor's brain better predicted that recorded from the learner's brain than vice versa. Together, these results indicate that social interactive learning can be neurophysiologically characterized in terms of IBS. Furthermore, they suggest that the learner's involvement in the learning experience, alongside the instructor's modeling, are key factors driving the alignment of neural processes across learner and instructor. Such alignment impacts upon the real‐time acquisition of new information and eventually upon the learning (behavioral) performance. Hence, besides providing a biological characterization of social interactive learning, our results hold relevance for clinical and pedagogical practices.