The UUA's founding traditions — Unitarianism and Universalism — emerged in explicit rejection of the doctrine of the Trinity. Classical Unitarianism held that God is strictly one person (the Father) and that Jesus was a great human teacher and moral exemplar but not the second person of a divine Trinity. The name 'Unitarian' itself derives from this affirmation of God's absolute oneness as opposed to Trinitarian theology.

However, the contemporary UUA is non-creedal: it imposes no doctrinal test on its members, including no requirement to affirm or deny the Trinity. Many UUA members identify as humanists, atheists, pagans, or non-Christian theists and do not engage the question of the Trinity at all. Among the minority who identify as Christians within the UUA, some affirm a form of liberal Christology while others retain the original Unitarian rejection of Trinitarian doctrine.

The UUA's Seven Principles — the closest thing to a shared statement of values — make no reference to God, Christ, or the Trinity. The UUA explicitly affirms 'a free and responsible search for truth and meaning' as a guiding principle, which means individual members are free to hold whatever theological views they find meaningful. The rejection of binding creedal authority means the UUA's relationship to the Trinity is defined more by the absence of affirmation than by formal denial.