The present study investigates the processes by which essentialist beliefs about religious categories develop. Children (ages 5 and 10) and adults (n = 350) from 2 religious groups (Jewish and Christian), with a range of levels of religiosity, completed switched-at-birth tasks in which they were told that a baby had been born to parents of 1 religion but raised by parents of another religion. Results indicated that younger children saw religion-based categories as possible essential kinds, regardless of the child's own religious background, but that culture-specific patterns emerged across development. This work shows that cultural context plays a powerful role in guiding the development of essentialist beliefs about religious categories.