We meta-analytically investigated the strength of synchrony on four dimensions of response: (1) prosocial behavior, (2) perceived social bonding, (2) social cognition, and (3) positive affect. A total of 42 independent studies (N=4327) were analyzed in which experimentally manipulated synchronous actions were compared to control conditions in healthy non-clinical samples. Our random effects model indicated that synchronous actions affected all four dimensions of response. Synchrony had a medium-sized positive effect on prosocial behaviors, a small-to-medium-sized positive effect on both perceived social bonding and social cognition, and a small-sized positive effect on positive affect. Notably, synchrony in larger groups increased prosocial behavior and positive affect, but group size did not moderate the relationship between synchrony and perceived social bonding and social cognition. This pattern suggests that distinct process mechanisms (neurocognitive versus affective) might underpin synchrony's effects on dimensions of response as a function of group size. •Synchrony increases cooperation, social connection, partner perceptions and affect.•Distinct process mechanisms likely underpin synchrony's effects on these outcomes.•Group size moderates the relationship between synchrony and outcome variables.