After the collapse of Communism, a major overhaul of the systems of religious governance took place in Bulgaria and Russia. Policies of liberalisation were pursued in both states which created conditions for the revival of religion and growth of religious diversity. This research article analyses the state approaches and policy orientations characterising the governance of religious diversity in Russia and Bulgaria in the post-Communist years as well as challenges to the fulfilment of religious freedom and religious equality. Using the lens of religious nationalism, it demonstrates that religious nationalistic tendencies are significant in both states when it comes to the governance of religious diversity. Furthermore, the analysis suggests that such tendencies are inscribed in a contradiction between constitutionally-established principles and nationalism-tainted practices when it comes to the treatment of some minority religions or/and groups.