From the Second Vatican Council and particularly from the decree Optatam Totius, a renewal of Moral Theology was requested in three basic guidelines: the rescue of the biblical tradition, the accent in the Salvation History and the link with the Liturgy. Such renewal is urgent and necessary in meeting the many challenges to talk theologically about the sexuality in post-modernity. Because of that, the mystagogy of Christian Initiation is presented as a way to simultaneously meet the Second Vatican Council appeals and speak a language accessible to postmodern human being. It is, in effect, from a mystagogical approach to the Rite of Christian Initiation of Adults that several implications for the ethics of sexuality such as communicability, relationality, creativity, fertility, playfulness, responsibility, nuptiality, etc., are revealed. Such implications extend the horizon of possibility to address the ethics of sexuality theme in post-modernity, while redirect this theological discipline to the centrality of the Paschal Mystery of Christ.