In recent years, religions - especially the evangelical ones - have been gaining space in the public debate in Brazil. There are openly religious representatives in the National Congress, in the Supreme Court, and in the most varied spheres of power. The prison system, which is also inserted in society, has not gone unpunished by the religious advance. In recent years, evangelical Christian religions have gained space and prominence in the prison scenario through religious assistance - which is a constitutional right of every prisoner. Given this scenario, the objective of this study is to understand how religions operate and how their discourse echoes in the prison environment, given the constitutional limits imposed by the 1988 Federal Constitution and other national and international legal frameworks. The research combines literature review, official documents and statistical data from official sources - themes such as secularism, secularization, legal order, prison system, Pentecostalism and religions are important and determining factors for this research - in addition to data and information collected from the prison unit Penitenciária Professor Ariosvaldo Campos Pires, in Juiz de Fora, which is the main referential focus of this research. This unit, as is the case with most prisons in Brazil, has a wide variety of religious denominations that provide assistance to its prisoners. This contribution allows us to analyze the modus operandi by which the entities involved with chaplaincy act within the system - both before and after the Covid-19 pandemic. In this sense, this field is yet another social sector that is being occupied by the growth of religions, their discourse and performance. This research has shown, however, that there are constitutional limits to be respected, even within the religious freedom that each individual enjoys. Jailed or not.