Music is widely acknowledged to have social efficacy at the group level. This effect is hypothesised to be underpinned at least in part by entrainment. During collective musical behaviours, entrainment – the shared synchronisation of internal oscillators – is suggested to afford the perception of actions, intentions and motivational states as joint action, shared intentionality and mutual motivational states, which in turn fosters interpersonal affiliation and prosocial behaviours, including trust. However, it is unknown whether entrainment’s effects on prosociality persist when we are passive observers. In this study, 44 participants (21 women; average age = 28; average years of musical training = 10) watched audio-visual tokens in which a) the footsteps of an actor were entrained (synchronised) with a drumbeat, b) the footsteps were disentrained (unsynchronised) with the drumbeat and c) the soundtrack was grey noise (control condition). Participants were subsequently required to decide if the actor was engaged in a trustworthy or untrustworthy activity. Results show that participants were more likely to judge the actor as trustworthy in the entrain condition than the disentrain condition, but that the entrain condition was not significantly different to the control condition. Furthermore, this pattern of results was only found for a subgroup of the stimuli. There were no effects of age, gender or musical training. Given the nature of the task, which encourages passive entrainment rather than active movement, these findings indicate that the prosocial outcomes of musical engagement may be more common and have a broader significance than previously suggested.