Between 2015 and 2021, almost all Brazilian federal universities adopted hetero-identfication procedures as part of the eligibility criteria for admission in undergraduate courses through racial affirmative action. This paper examines how and why this happened, mobilizing the literature on organizational isomorphism and social movements. Based on the analysis of a diverse set of documents and interviews, we argue that such a diffusion was propelled by coercive, mimetic, and normative mechanisms that involved the agency of Black students, organizations of the Black movement, faculty and staff, and professionals in state agencies, all engaged to protect racial affirmative action. The diffusion of hetero-identification procedures has transformed the way in which the right to affirmative action is understood and has brought about organizational change in the admission process and in other aspects. Implications for the study of change in higher education and of race relations in Brazil are discussed at the end.