Biblical Unitarians, in common with virtually all modern biblical scholars and textual critics, hold that Mark 16:9-20 (the Longer Ending) is not part of the original text of Mark's Gospel. The two earliest and most reliable Greek manuscripts (Codex Sinaiticus and Codex Vaticanus) end at Mark 16:8, and ancient church fathers like Eusebius and Jerome note that this passage was absent from earlier manuscripts.

The Longer Ending exhibits stylistic and vocabulary differences from the rest of Mark, and its content (resurrection appearances, a commission to preach, miraculous signs) parallels accounts in Luke, John, and Matthew rather than Mark's own narrative style. Biblical Unitarians view this as a textual historical matter of scriptural authenticity that does not depend on theological commitments, though they note that the resurrection accounts in the Longer Ending need not presume Trinitarian Christology.