Interculturalism has recently gained attention in discussions of migration-related diversity governance, particularly in the post-secular context. While it has been discussed in fields such as education and international relations, its application as a city strategy for diversity governance is relatively new. The understanding of interculturalism as an approach to the socialisation of citizenship emerged a decade ago by professionals and experts and has been promoted by the Council of Europe’s Intercultural Cities Programme since 2008. However, there is an ongoing debate about how interculturalism should deal with religious diversity, which is currently limited compared to multiculturalism. This article critically asks whether this approach should be extended to address religious claims in liberal and democratic post-secular societies. After an initial overview of how religious diversity and interculturalism have been addressed in the Council of Europe and, more specifically, in the field of education, four key indicators will be derived that will allow us to assess first the Intercultural Cities programme and then Barcelona’s emerging post-secular approach, which will be seen as a laboratory for managing religious diversity through an intercultural lens.