In intersectionality studies, debates about the additive versus constitutive nature of intersectionality are long-established. This article attempts to intervene in these conversations by examining how additive, “diversity within” intersectionality works in practice. Across feminist academia, advocacy, and policymaking, there is a widely held perception that among the nongovernmental organizations constituted around identity-based inequalities (feminist, racial justice, migrants, disability, and LGBTQI+ rights), it is the feminist sector that best advocates for and attempts to practice intersectionality. This is related to the appropriation of Black feminist theories of intersectionality which emerged from grassroots activism and Critical Race scholarship as “feminist” theory, wherein feminist is always-already constructed as white. Drawing on empirical research with equality organizations working with disabled women and trans women in England and Scotland, this article suggests that the opposite is true: the additive intersectionality practiced by the white-led feminist sector serves to uphold white supremacy and other structural inequalities.