Bridging the literature of procedural justice, social identifi cation, and voice, we present a conceptual model of observers' voice responses to injustices perpetrated on coworkers. Based on social identity theory, we contend that similarity to the target of injustice infl uences observer identifi cation with the target, as moderated by the observer's scope of justice, which then infl uences the observer's perceptions of injustice and decision to express voice. Additionally, we posit that the link between observers' perceptions of injustice and expressed voice is moderated by the observer's perceived opportunity to express voice. Finally, we propose that the decision to express voice individually or collectively depends on the justice climate along with the costs and benefi ts associated with each option. Theoretical and managerial implications are discussed.