Dunlap was launched 18 April 1936 by United Shipbuilding and Dry Dock Corp., New York N.Y., sponsored by Mrs. Robert H. Dunlap, widow of Brigadier General Dunlap; and commissioned 12 June 1937, Commander A. E. Schrader in command.

Dunlap operated along the east coast on training duty, and in June 1938 served as escort at Philadelphia for SS Kungsholm, carrying the Crown Prince of Sweden. On 1 September she got underway for the west coast; except for a cruise to the Caribbean and east coast for a fleet problem and overhaul in the first 6 months of 1939, Dunlap served along the west coast until 2 April 1940 when she sailed for Pearl Harbor, her new home port.

On 7 December 1941 Dunlap was at sea bound for Pearl Harbor with TF 8 after ferrying planes to Wake Island. She entered Pearl Harbor next day and patrolled in the Hawaiian area until 11 January 1942 when she sortied with TF 8 for air strikes on the Marshalls, returning 5 February. After taking part in the raid on Wake Island of 24 February, she continued to patrol in the Hawaiian area until 22 March, then escorted convoys between various ports on the west coast until returning to Pearl Harbor 22 October 1942.

Dunlap arrived at Nouméa, New Caledonia, 6 December 1942 and operated from that base on training and patrol duty, and as escort for convoys to the Fiji, Tonga, and New Hebrides Islands until arriving at Guadalcanal 30 July 1943 for duty in the Solomons. On the night of 6-7 August she was sent with five other destroyers to intercept a Japanese force carrying reinforcements to Kolombangara. In the resulting Battle of Vella Gulf, a brilliant night torpedo action, the ably handled task group sank three Japanese destroyers and drove the fourth back to its base at Buin. They suffered no damage themselves. (continued)