This study focuses on Muslim fertility in Europe. Evidence from 25 countries suggests that the Muslim total fertility rate is on average 47% higher than the national level. However, we find a significant difference in the level of fertility of native-born Muslims and immigrant Muslims. The native-born have a 19% higher total fertility rate,while immigrants have 62% higher fertility. Our main research question is whether religion is an important determinant of fertility outcome, or whether the other characteristics that are specific for Muslims in Europe (e.g. socio-economics, migrant status, and religiosity) determine the observed difference in fertility. To answer this question, we focus on three case studies: Spain, where most Muslims are immigrants; Bulgaria, where most Muslims are native; and Greece, which has significant shares of both recent migrants and native Muslims. Our findings suggest that the immigrant status of Muslims and their socio-economic status are more important than religion in terms of explaining their high fertility.