After shakedown, McDougal operated directly under the office of the Chief of Naval Operations until mid-1937, when she steamed to the Pacific for duty with the scouting force and Inter the battle force. Operating out of San Diego, she served as flagship for Destroyer Squadron 9. As a heavily armed destroyer leader, she took part in type training, readiness cruises, and battle problems in the eastern Pacific and in the Caribbean operating area.
McDougal returned to the Atlantic coast with her division in the spring of 1941 to operate along the east coast. Between 5 and 7 August she escorted Augusta (CA-31) carrying President Franklin Roosevelt to Placentia Bay, Newfoundland, where, from 9 to 12 August, he met Prime Minister Winston Churchill for the first time to discuss the menace of the Axis Powers and to formulate "common principles" for peace in the postwar world. On 10 August McDougal transported President Roosevelt to and from HMS Prince of Wales during the only meeting of the two leaders on board the ill-fated battleship. The President and the Prime Minister completed formulation of the eight-point declaration, embodied in the Atlantic Charter, 12 August: thence, both British and American ships departed Argentia later that day. McDougal screened Augusta to the coast of Maine 14 August before resuming operation along the eastern seaboard.
Assigned to convoy escort duty in the South Atlantic, McDougal steamed for Capetown, South Africa, from the Caribbean early in December. While battling heavy seas off Cape of Good Hope, she received news of the Japanese attack on Pearl Harbor. She returned to Trinidad 30 December; thence, she departed for patrol duty off the South American coast 18 January 1942. During the next several months she carried out patrol and escort duty between Brazilian and Caribbean ports; and, following overhaul at Charleston during July and August, she cruised via Caribbean ports to the Panama Canal where she arrived 31 August.
Assigned to the Southeast Pacific Force, McDougal began patrol duty along the Pacific coast of Latin America 7 September. During the next 2 years she cruised out of Balboa, Canal Zone. north to Nicaragua and south to the Straits of Magellan. She patrolled the southeast Pacific westward to the Galapagos and Juan Fernandez Islands and touched coastal ports in Ecuador, Peru, and Chile. She returned to New York 4 September 1944.
Resuming convoy escort duty 12 September, McDougal sailed for the United Kingdom in the screen of convoy CU-39. During the next 6 months she made four round trips between New York and British ports; and, after arriving New York 5 March 1945 with ships of UC-57, she sailed the same day for overhaul at Charleston.
She cruised to Casco Bay 11 to 15 September and began support duty with the Operational Development Force, Atlantic Fleet (TF 69). Reclassified AG-126 on 17 September, she carried out experimental operations helping to improve naval gunnery and radar. Her duties during the remainder of 1945 sent her to Boston, Newport, and Norfolk. She arrived Boston 15 December, thence resumed operations out of Norfolk 29 March 1946. She steamed to New York 15 to 16 June and decommissioned at Tompkinsville, Staten Island, 24 June 1946.
Assigned to duty as a training ship for Naval Reserves, McDougal was placed in service 13 January 1947. She operated under control of the 3d Naval District while based at Brooklyn, N.Y. She was placed out of service 8 March 1949 and sold to H. H. Buncher Co., Pittsburgh, Pa., 2 August. Her name was struck from the Navy list 15 August, and she was as removed from naval custody 22 September 1949.