Ann Thomas Griffin (A.T.) Johnston served as the Acting Assistant Secretary of Defense for Legislative Affairs. In this role she supported the Secretary of Defense in executing the organization's mission of promoting the policies, strategies, and budget of the Department of Defense to the United States Congress. 

Prior to assuming the role of the Acting Assistant Secretary of Defense for Legislative Affairs, she served as the Principal Deputy Assistant Secretary of Defense for Legislative Affairs. She was responsible for managing a myriad of legislative activities to support the Department of Defense's legislative priorities with Congress, including direct support to the Deputy Secretary of Defense.

Before joining legislative affairs, she served as Deputy Assistant Secretary of Defense for Military Community and Family Policy from February 2018 to February 2020.  In that role, she was responsible for a broad portfolio supporting the Secretary’s fourth line of effort in the National Defense Strategy that included policy, advocacy, and oversight of all community support to service members and their families.

Prior to joining Military Community and Family Policy, Mrs. Johnston served as senior policy advisor to the House Energy and Commerce Committee focusing on both energy and environmental policy. Before joining the Committee, she served as Deputy Chief of Staff and Policy Director for Congressman Lee Terry of Nebraska.
Mrs. Johnston previously served in the White House as a Special Assistant to President George W. Bush in the Office of Legislative Affairs, overseeing coordination with the Senate, including the Energy and Natural Resources Committee, Environment and Public Works Committee, and the Commerce Science and Transportation Committee.

She was appointed Deputy Assistant Secretary for Legislative Affairs at the US Department of Energy in 2001, serving as the conduit for the Secretary of Energy to the Congress.

Prior to joining the Bush Administration, Mrs. Johnston worked for then Congressman Richard Burr managing a diverse portfolio of issues. Mrs. Johnston also worked in the private sector for two Fortune 200 Companies and two government affairs consulting firms.

Mrs. Johnston is from Wilson, North Carolina, and is a graduate of Wake Forest University. She lives in Alexandria, Virginia with her husband.  Her daughter attends Hillsdale College. Her son and daughter-in-law serve as 2nd Lieutenants in the United States Army.