Coordination with others in groups is crucial to group cohesion and function, yet only scant research addressed behavioral and physiological interpersonal synchrony in groups during shared activities. We present data from 39 triads instructed to drum together. Based on video-recordings of the task and participants' electrocardiograms, we computed physiological synchrony in cardiologic interbeat intervals and behavioral motion energy synchrony among group members as they were drumming together. Overall, behavioral and physiological synchrony were positively associated with continuous shifts from positive correlations to non-significant ones throughout the task. Results shed light on the relational components of group bonding and elucidate the dynamic interactions between physiological and behavioral synchrony at the group level.