This thesis is a comparative analysis of the doctrine of deification in sacramental worship as taught (and practiced) by the Eastern Orthodox and Latter-day Saint (Mormon) churches. The doctrine that man may become like God—known as deification, divinization, or theosis—is a central teaching in the Orthodox and Mormon traditions. Both faiths believe that man may become like God. However, because of doctrinal presuppositions and disagreements regarding the natures of God and man, Orthodox and Mormon teachings of deification do not mean the same thing. This thesis will outline several key distinctions between their respective doctrines. And yet, despite doctrinal disagreements, this thesis will also illustrate how Orthodoxy and Mormonism share several notable similarities regarding the function of sacramental worship in the process of theosis. Mormonism and Orthodoxy both believe that men and women may achieve theosis only as they interact with God. Through the combined initiatives of the Father, his son Jesus Christ, and the Holy Ghost, humankind may receive the attributes of divinity and participate in the process of deification. The means whereby humanity may interact with God are through sacramental participation. This thesis will illustrate how institutional rituals and personal worship practices foster man's divine interaction and ultimate deification. Furthermore, Orthodox and Mormon rituals are deeply rooted in the doctrine of deification—each ritual contributing to man's divine transformation. As such, those rituals reflect numerous thematic variations and emphatic differences of their respective traditions. This should not discourage the reader from comparing Orthodox sacraments with Mormon sacraments; rather, as one studies the similarities and differences in the Orthodox and Mormon sacraments, he or she will begin to see how deification is so intricately woven into the worship practices of these two faiths.