Whilst reports of value tensions between new managerialism and Catholic education have emerged as a key theme in the academic literature, there remains little empirical understanding of how teachers negotiate these complex terrains in Catholic schools. Drawing on qualitative data from teachers in two Catholic post-primary schools in Northern Ireland, this paper sought to explore how Catholic teachers developed a distinctively Catholic ethos against a culture of "creeping managerialism". The paper has shown that despite the predominance of managerial practices, tensions between managerialist values and the "Catholic ethos" did not emerge in either context: in one school managerialism permeated the school and the Catholic ethos was constructed within this context. In the other school a staff process of spiritual renewal had consolidated a commitment to the Catholic faith and social inclusion. It was argued that the dialogical engagement around Catholic values may help Catholic schools defend against the harsher manifestations of managerialism without compromising the pupils' capacity to realise their academic potential.