Immigration from the Global South is a recent phenomenon in Italy, which is turning from a prevalently homogenous Catholic country into a multi-faith one. This transformation is evident too in prisons, where people from different religious traditions share space. The long road from religious diversity to social acceptance of differences is difficult. The public debate concerns essentially Muslim inmates, and the arguments swing from ‘securitarian’ views to an inclusive approach as an alternative way to prevent radicalisation. The lack of meaningful relationships between inmates of different faiths and their religious communities can be a serious obstacle to social reinsertion. An analysis of the Italian prison system with statistical data and qualitative research enables us to outline a model of the evolution of the penitentiary systems.