Eastern Catholic churches affirm the Chalcedonian definition of Christ's person: Jesus Christ is one divine person possessing two complete and unconfused natures—fully divine and fully human—united without mixture or separation. This was solemnly defined at the Council of Chalcedon (451) and is professed in every Divine Liturgy.

Mary is venerated as Theotokos (God-bearer or Mother of God), a title affirmed at the Council of Ephesus (431) and central to Eastern Christian piety. The Eastern tradition richly develops Christological themes in its hymnography, iconography, and theology, presenting Christ as the New Adam who restores human nature and makes theosis possible.