Research on perceptions of discrimination has focused on group-based differential treatment that is widely accepted as being illegitimate (e.g., based on race or gender). The present research investigates how individuals interpret less obvious forms of group-based exclusion based on age (Study 1) and vision correction status (Study 2). We propose that individuals will not question the legitimacy of such treatment, unless they are provided with explicit cues to do so. Participants who merely encountered exclusion (baseline control) did not differ from those who were directed to consider the legitimate reasons for this treatment, with respect to perceived legitimacy, felt anger, and collective action intentions. In contrast, individuals who were directed to consider the illegitimate reasons for the exclusion perceived it to be less legitimate, felt more anger, and reported higher collective action intentions. Participants’ own status as potential victims or mere observers of the exclusion criterion did not influence their legitimacy perceptions or felt anger. Results suggest that when confronted with forms of group-based exclusion that are not commonly defined as discrimination, people do not perceive an injustice unless explicitly directed to seek it out.