Team decision-making can go wrong when individuals fear to voice suggestions or concerns to higher status team members. We investigate how after-event reviews (AERs) can be used to promote voice behaviour and hierarchy-attenuating beliefs in multi-professional action teams. We hypothesized that (1) lower status team members will speak up more following an assertiveness-specific AER (ASAER) as compared to a teamwork-generic AER (TGAER) and (2) that an ASAER leads to stronger endorsement of hierarchy-attenuating beliefs than the TGAER. To test these hypotheses, we implemented simulations of medical emergencies with 20 healthcare teams consisting of low (i.e., nurses) and high-status (i.e., physicians) professions. After participating in one of the two AERs, teams managed a simulation in which a higher status confederate engaged in potentially harmful actions. Behavioural coding of the videotaped simulations and assessment of team members’ hierarchy beliefs supported both hypotheses: nurses spoke up more following the ASAER than following the TGAER and both professional groups reported significantly higher levels of hierarchy-attenuating beliefs following the ASAER as compared to the TGAER. We discuss how AERs can affect upward voice and increase awareness for the potential downsides of status hierarchies in multi-professional teams.