In 2 studies, we examined the influence of in-group norms of anti- and pro-discrimination on prejudice and discrimination as a function of intergroup similarity (Studies 1 and 2) and in-group identification (Study 2). Intergroup similarity decreased prejudice and discrimination when in-group norm prescribed discrimination, whereas it increased prejudice and discrimination when in-group norm proscribed discrimination (Study 1). This pattern was most apparent in highly identified in-group members (Study 2). The paradoxical effect of the anti-discrimination norm in the high similarity condition (i.e., an increase in discrimination) is interpreted as a response to the threat this situation introduces to in-group distinctiveness.