Radical ethnonationalism has drastically risen in Western politics, largely mobilized by nostalgia for the country's past with homogeneity and Christianity as a cultural symbol against non-Western immigrants, especially Muslims. However, how nostalgia for Christianity's past significance can invoke anti-Muslim sentiments is unknown, especially given that Christianity is increasingly losing its previous status under secularization, resulting in radical backlash from the Christian right. In the current study, I examine whether nostalgia related to religion and the religious–secular gap in the perceived status of religion can induce anti-Muslim attitudes among Christians from 20 Western countries using International Social Survey Programme data and mixed-effect multilevel modeling. Contrary to expectations, anti-Muslim attitudes are stronger for people with higher levels of Christian religiosity and doctrinal belief, and exclusivist view on religion, when they have less religious nostalgia by perceiving a stronger status of religion. Moreover, in countries with a larger religious–secular gap in the perceived status of religion, people holding exclusivist views on religion are more hostile to Muslims. Yet, the findings can still be consistent with theoretical expectations, since anti-Muslim attitudes are likely promoted through backlash from the Christian community against religious diversity, expressed in demands for a larger salience of religion rather than nostalgia.