This study examines the role of religion in Turkish and Israeli nationalism and national identities. It studies whether religion is an important factor in foundation and sustainment of Turkish and Israeli nationalisms. Although many works of nationalism studies have focused on Turkish and Israeli nationalism, there is not an emphasis on religious nationalism, which is an emerging literature criticizing the secular attempts to define a nation. Religious nationalism literature argues that religious and national identities are fused together in the nation-state, where the state is the primary actor mobilizing these identities. Therefore, I do not refer to ethnic and religious minority movements but I take official ideology and foundational moments of the nation-state as "religious nationalism". The study focuses on two time periods: the foundation of the new nation-states as Turkish Republic in 1923 and state of Israel in 1948; and the period after the turn of the 21st century. First, it examines how religion manifests itself in the foundational moment of the new nation-states: as "the heroic Muslim Turk" against "the occupier Christian identity" during the World War I and the Independence War in Anatolia, as well as the migrations to the lands of Palestine have contributed to a distinctly religious understanding of the Israeli national identity. Secondly, both states have maintained religious versions of their national identities and fostered them especially in the 21st century. The Justice and Development Party government in Turkey, and the Likud Party in Israel have contributed to religious understandings of what it means to be a national citizen in their states through political discourse, socio-economic investments and education policies. The study provides a challenge to mainstream modernization and secularization theories dominating theory of social sciences, especially in the field of nationalism studies.