Following an extensive shakedown cruise to Europe and western South America, Macdonough Joined the Pacific Fleet and operated out of San Diego until 12 October 1939. She then shifted to a new home port, Pearl Harbor as part of Destroyer Squadron 1. In port 7 December 1941, Macdonough splashed one of the Japanese attack plane before heading out to sea to Join others in the search for the enemy task force. For the next 3 months, the destroyer performed scouting assignments southwest of Oahu. Before returning to Pearl Harbor to escort convoys to and from west coast ports, she steamed as far as New Guinea, lending support to air strikes on Bougainville, Salamaua, and Lae.
Macdonough returned to the western Pacific to prepare for the Guadalcanal invasion Operating with Saratoga, she provided cover for the landings on Guadalcanal and Tulagi, 7 August 1942. She remained in the area, taking part in the Battle of Savo Island and fighting enemy aircraft and shipping during the landing of reinforcements on the island. At the end of September, she commenced escort work, plying between New Guinea, Espiritu Santo, and Pearl Harbor until reporting to Mare Island, 22 December, for overhaul. (continued)