Congregational polity is the defining characteristic of this tradition. Each local congregation is fully autonomous — self-governing, self-supporting, and self-propagating — directly under the authority of Christ as its sole head. No higher ecclesiastical body (association, conference, or general synod) has binding authority over a local congregation in matters of faith, worship, or order. The Cambridge Platform (1648) established this principle for New England Congregationalism, and it has been foundational ever since.

The United Church of Christ maintains this congregational principle in its Constitution, which affirms the 'autonomy of the local church.' The UCC General Synod, conferences, and associations act through persuasion and consensus, not legislative mandate binding on congregations. This is why individual UCC congregations vary so widely in theology and practice — there is no mechanism to enforce doctrinal uniformity. At the same time, the UCC structures provide resources, fellowship, and collective prophetic witness. The national denomination has taken strong stances on social justice issues (racial reconciliation, LGBTQ+ inclusion, environmental justice), which influence but do not bind member congregations.