This article explores the theme of religious socialisation in an environment marked by modernity. It has three goals: first, to analyse the changes in religious socialisation across age groups; second, to analyse the impact of religious socialisation on religiosity; and third, to analyse the impact of religiosity on religious socialisation. Based on quantitative data about the Lisbon Metropolitan Area, results show the following: The level of religious socialisation increases with age, but young respondents have been significantly less socialised than older age groups; the level of religious education provided by respondents to their children increases with age; socialisation and religiosity are biunivocal, mutually reinforcing. In short, this article reinforces the theory of cohort replacement, which states that religiosity decreases in younger groups due to the decrease in religious socialisation over time.