Cyril of Alexandria's Festal Letters are an underutilised source of his theology. Through them one can trace the development of his thought throughout the tumultuous years of his episcopacy. In this article, I draw attention to Cyril's ‘unitive’ Christology and the way he explains the incarnation to those under his pastoral care. Cyril employs key strategies informed by strong theological convictions to describe Christ as one subject who is fully divine and human.