<p>In social robotics, interaction synchrony plays a central role in creating intentional and lifelike robotic agents. However, is yet to be studied the extent to which interaction synchrony is a relevant social aspect used by external observers to make inferences about human–robot dyads. For instance, whether external observers evaluate the human–robot ability to work as a team. In one mixed-design experimental study, 34 participants were presented with two videos showing a human–robot dyad engaging in a synchronous vs. asynchronous interaction. We found evidence that the mere perception of synchronous interactions predicts external observers’ estimations of the dyad’s collective efficacy, fluency, and cohesion. Our findings also suggest that seeing asynchronous interactions after synchronous ones elicits greater differences in participants’ estimations, compared to when participants see asynchrony first. Unexpectedly, synchrony did not play a significant role in shaping participants’ affiliation intention towards the dyad. Overall, our findings speak to the importance of synchrony in shaping the way humans observe a human-robot dyad and think about their collaborative capabilities. Not only do we provide new insight into the way humans perceive social groups that include at least one robotic agent, but we also draw broader implications to the human–robot interaction field.</p>