Most European countries accept the necessity of school based Religious Education (RE). In Ireland, where almost 89% of primary and 47% of second level schools have a Catholic patron, the Catholic Bishops recognise the importance of RE in holistic education and uphold RE as an expression of school ethos. However, in an increasingly diverse society with rapidly falling numbers of people who identify and practice as Catholic, can the provision of RE in Catholic schools be sustained into the future? This paper examines the results of the first large scale, mixed methods empirical study into Catholic school (primary and secondary) ethos in the Republic of Ireland, of which Religious Education is an essential dimension. Through an examination of survey and semi-structured interview data from teachers and leaders, it analyses their views and experiences of RE and highlights the role and reality of RE in Catholic schools in Ireland today. Findings demonstrate a level of commitment and professionalism among stakeholders, and much in the way of good practice and commitment to the subject. However, they also indicate that support for RE as a subject, and for RE teachers and leaders, is urgently needed. Without ongoing, high-quality support for teachers, and systematic evaluation of the teaching and learning of RE, the future of RE in Catholic schools in Ireland looks bleak. While the study is carried out in Ireland, it is also of interest to other jurisdictions where schools are faced with similar challenges and to Catholic education systems looking to the future of Religious Education.