Interculturalism (IC) is presently discussed as a foundational basis for local public policy aimed at managing migration-related diversity within ethno-culturally plural societies, especially at the local level. Despite its increased saliency over the last decade, IC is neither theoretically new nor was it always intended for mere application in strictly city contexts of diversity. Rather, it has a global origin as a political basis for international relations and negotiations. In discussing these origins, this article has two main interrelated aims. Firstly, it provides an overview of the multi-scale approach of IC, with the purpose of disentangling analytically the different empirical bases where it can frame the diversity agenda. Secondly, it explores whether a lack of appreciation and awareness of this multi-scale orientation may affect IC’s capacity to address the challenges of diversity governance at the local level. Methodologically, the article will undertake a textual analysis of a select number of leading documents framing its practice within the broader policy literature produced by the four main institutions that have advocated the intercultural approach within a global agenda. These are the United Nations Educational, Scientific and Cultural Organization (UNESCO) and United Nations University, on one hand, and the European Union and the Council of Europe on the other. The main findings show us the importance of a multi-scale thinking in diversity and IC studies, to avoid contributing to greater confusion in its applications.