This article overviews the contemporary context for teaching Religious Education (RE) in Ireland and profiles changing religious demographics in an increasingly secular context. It presents the findings of a two-year mixed-methods study undertaken in two third-level Catholic colleges in Ireland, investigating four hundred third-level Initial Teacher Education (ITE) students' perceptions of the religiously unaffiliated. The research data reveals the complexity and ambivalence of ITE students' attitudes to teaching RE in primary schools in a rapidly changing Irish society where one in ten is religiously unaffiliated (Central Statistics Office, 2017). Several challenges emerge for ITE students as they begin teaching RE in Ireland's denominational primary school context. The religious and convictional perspectives of the sample group are profiled and findings reveal that participants' personal worldviews impact on their understandings of their future professional roles as religious educators. Data from this mixed methods research suggest that while ITE students view the teaching of RE as an important professional duty, a disconnect between their own personal beliefs and the curricular content they are required to teach in sacramental RE programmes in Catholic primary schools creates a climate of ambivalence and uncertainty.