The denial of Christ's pre-existence as a divine being is one of the most foundational and defining commitments of Biblical Unitarianism. Jesus of Nazareth did not exist before his conception in Mary's womb — he was not a pre-existent divine person who became flesh. Before his birth, Jesus existed only in the foreknowledge and purpose of God: in God's plan and intention, not in personal reality.

Biblical Unitarians invest considerable exegetical effort in reinterpreting the texts typically used to support pre-existence. John 1:1-14 is read as describing the creative word or wisdom of God (personified in Jewish fashion) that was embodied in Jesus, not as a personal pre-existent being. John 8:58 ('Before Abraham was, I am') is interpreted as Jesus speaking in terms of his preordained status in God's plan. Philippians 2:6-7 ('who, though he was in the form of God, did not count equality with God a thing to be grasped') is read as describing Jesus' human character as the image of God — not a pre-incarnate divine state.

This denial of pre-existence is the primary point of distinction between Biblical Unitarians and the Arian tradition, which held that Christ pre-existed as a divine (but subordinate) being created before the world. Biblical Unitarians typically deny any form of pre-existence — personal, spiritual, or otherwise — holding that the first moment of Jesus' existence was his conception by Mary.