The importance of social connection to well-being is underscored by individuals' reactivity to events highlighting the potential for rejection and exclusion, which extends even to observing the social exclusion of others ("vicarious ostracism"). Because responses to vicarious ostracism depend at least in part on empathy with the target, and individuals tend to empathize less readily with outgroup than ingroup members, the question arises as to whether there is a boundary condition on vicarious ostracism effects whereby individuals are relatively immune to observing ingroup-on-outgroup ostracism. Of particular interest is the case where members of a dominant ethnic group observe fellow ingroup members ostracize a member of a disadvantaged ethnic minority group, as here there is a compelling potential alternative: Perceived violation of contemporary social norms condemning prejudice and discrimination might instead lead dominant group members to be especially upset by "dominant-on-disadvantaged" ostracism. Accordingly, the present research examines, across four studies and 4413 participants, individuals' affective reactions to observing dominanton-disadvantaged versus dominant-on-dominant ostracism. In each study, dominant group members (White/Europeans) observed dominant group members include or ostracize a fellow dominant group member or a disadvantaged ethnic minority group member (a Black individual) in an online Cyberball game. Results revealed that dominant group members felt more guilt, anger, and sadness after observing severe ostracism of a disadvantaged as opposed to dominant group member. Although no direct effects emerged on behavioral outcomes, exploratory analyses suggested that observing ostracism of a disadvantaged (versus dominant) group member had indirect effects on behavior via increased feelings of anger. These results suggest that observing ostracism may be a sufficiently potent and relatable experience that when it occurs across group boundaries it awakens individuals' sensitivity to injustice and discrimination.