Cyril of Jerusalem, as catechist and mystagogue of his fourth-century See, focused on the orthodox formation of those in his care so that they would be able to live into their new identity as baptized and communing members of the catholic church. Of particular interest to Cyril is the transformative relationship between the Triune God and Christians; what he presents of his theology thus focuses on the relational dynamics within the Godhead as it pertains to sacramental theōsis. In this paper, I focus on Cyril's explicit and implicit use of the concept "like nature resting upon like nature" as the means for humans to participate in the divine nature. I demonstrate that Cyril's consistent and highly nuanced use of homoios is foundational to his expression of a Trinitarian theology which informs his sacramental theology. In particular, his use of the noun homoios is the means by which he carefully attends to the mystery of the unity of the divine nature of the Godhead while preserving the distinctiveness of the three persons (hypostases) within the Godhead. While Cyril only uses the phrase "like nature resting upon like nature" in his description of the Holy Spirit's descent upon Jesus at his baptism, I propose that this concept is central to his teachings on how, through baptism and eucharist, the Holy Spirit mysteriously sanctifies and deifies the catechumens so that they are transformed into faithful Christians.