The UUA holds no binding position on the nature of God and does not require belief in God as a condition of membership. A 2012 survey found that UU members include theists, deists, pantheists, panentheists, agnostics, atheists, and humanists. The UUA is one of the few religious bodies in the world that explicitly welcomes members regardless of whether they believe in God.

The UUA's Unitarian heritage emphasized the oneness and goodness of God — specifically against the Trinitarian doctrine — but this theistic framework has become just one option among many within contemporary UUism. 'God' is used by some UUs to mean a personal deity, by others to mean the ground of being (Paul Tillich's term), by others to mean the spirit of love and truth at work in the world, and by still others not at all. The UUA's worship resources include both explicitly theistic and non-theistic language to accommodate this diversity.

The UUA's sixth principle — 'the goal of world community with peace, liberty, and justice for all' — and its Seven Principles are framed in terms of human values and responsibilities rather than theological claims about God. This reflects the UUA's deliberate move from a specifically Unitarian-theistic identity to a broader humanistic and pluralistic one.