The UUA has a strong historic witness for peace and has generally been sympathetic to pacifism and conscientious objection to war. The UUA has passed General Assembly resolutions opposing specific wars (including the Vietnam War and the Iraq War) and affirming the rights of conscientious objectors. The UUA's commitment to justice, equity, and the dignity of all persons is in ongoing tension with the violence of warfare.

However, the UUA does not require pacifism of its members. Individual members hold diverse views on military service — from committed pacifists to those who support military service in what they regard as just causes. The UUA's non-creedal character means that military service is a matter of individual conscience and community discernment rather than denominational doctrine.

The UUA has historically maintained a close relationship with the peace movement and with organizations that support conscientious objectors. Many UU congregations participate in peace witness activities and support members who refuse military service on grounds of conscience. At the same time, UU members who serve in the military are not excluded from community or subject to discipline.